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Notes on Pottery Experiments in the 1770s


The following is a transcript of two note books (19 pages and 12 pages) written in the hand writing of James Caldwell (1759-1838).  The first is a record of experiments in pottery making and is similar to notes on other experiments recorded in James Caldwell's diary for the period 1770-1808.  The second notebook is headed Fossils but in fact gives a detailed description of various types of clays used for pottery making.  

It would appear that James started his career working for Josiah Wedgwood in the mid 1770s helping in the recording of experiments in pottery making.  It may be that James became a protégé of Josiah and that Josiah then introduced James to various people who were to become very influential in his life (Thomas Bentley, Thomas Sparrow, Thomas Stamford).  By 1783, at the age of approx 24, James was no longer working for Josiah Wedgwood but is recorded as being in partnership with Thomas Sparrow in the firm of Messers Sparrow & Caldwell, Attornies at Law.  It should be noted that when Josiah Wedgwood died in 1792 James Caldwell was his executor.  It should also be noted that in 1784 James Caldwell married Elizabeth Stamford, daughter of Thomas Stamford and niece of Thomas Bentley.

It is difficult to know why in 1790 James was writing out a series of notes on pottery experiments.  One reason might have been the fact that he was about to return to the pottery industry by going into business with Enoch Wood (1759-1840), the partnership of Wood & Caldwell coming into existence 1 January 1791.  Josiah Wedgwood's partner Thomas Bentley had died in 1780 and later on some of his possessions were to come to James Caldwell via Mary Bentley.  It may be that in 1790 or earlier Mary had given James some of the notes on experiments, which had somehow made their way into the possession of her late husband. 

These notes read as follows:


Observations and Experiments in Chemical Mineralogy 1790




Detached Specimens and Experiments from Loose Papers of Mr. T.B. [Thomas Bentley?]


An Historical Essay upon the Antiquity progress and present State of the Art of Pottery. 


The Great Estimation in which this Art was held by the Ancient and the various uses in which they employed its productions.

Instances in Statues Ornaments etc . . . Pliny.

The nations most famous for their works in clay.



Quality of the best porcelain by Pere De Combley.

Page 151

The fineness of the material

The whiteness (if intended for White)

The fine polish of the surface

The painting . . . .

The Designing of the figures

And the form of the vessels.



Merchants don't buy the fine China. See the Page and quotation. Merchants too apt to discourage the manufacturey for the sake of profit discouraged by a poor price at Court. Take the whole passage.


Painted Etruscan Vases


The art seemed to be declining in Pliny's time, and shared the fate of the other fine arts, and was again revived in the time of Raphael. Neglected again upon the introduction of Porcelain.

The defects of this earthen ware viz the softness of the body and the glaze. 




not sufficiently adhering to it, contributed to its decline. 


Delft Ware

The various imitations of Porcelain at Dresden, in France, England etc with their excellencies and defects.


The invention of finer earthen wares in Staffordshire how and by whom introduced with their various improvements to this time for use and ornament.


Encaustic Painting, its invention and uses.


Baso Relievos for Pictures, tablets, panels etc.


Medals and medallions of illustrious men to form a cheap historical cabinet.


Bible.. Homer . . Theophrastus Narro

            Strabo . . Atheneas

            Pauvanias . . Pliny

            Dionissius . . Halicarnasseus


            Ct. Caylus

            Pere D'entercelles History of China

            Mr. Hamilton

             Stanways Travels. Memoirs of Brandenburgh.




Nov.27 1768


Experiments. Hints and Memorandums


Experiment 1. Have cleaned and polished several of the brown teapots that had an ugly whitish scurf upon them, with skimmed milk. It gives them a good polish and leaves them of an uniform agreeable colour. I suppose this is the wash used to glaze pipes but there may be some particular manner of applying it. Q?


Experiment 2. One of these pots Gilt does not look amiss but the heat of the stove raises small scurf in the hollow parts. I suppose from the milk. This may be prevented by gilding the pots first and applying the wash afterwards.

Q?. Whether a little fine ground whiting or pounded clay should not be added to the milk, when it is applied to white biscuit.


Experiment 3. We have gilt two Etruscan vases, the gold comes to a better colour upon these than any other articles and has a fine rich effect, but might not the colour be still finer if it was laid in with a yellow size. I think the red size affects the colour of the gold upon all the ware. Would not then black vases have a good effect mounted, mottled and sprigged with silver as well as gold?


Experiment 4. Have ordered some black - to be washed over to try the effect of mechanical smallness produced that way.

To sprinkle biscuit ware with gold powder or Aura Mosaicum and glaze it over, especially dark coloured.


Cement for joining alabaster, marble, porphyry

 - and other stones - Dolpie.


Experitment 5. Bees Wax . . 2

Resin . . .1

Of the matter to be joined ground fine 1. ½ 


This recipe is taken from Hunchell and altered a little. I suspect for the worry See page . . . 402 . .


Melt the two first ingredients together, stew the powder into the melted mixture and stir it continually, pour the mass upon the water and knead it well in




the water immediately, that the powder may be perfectly incorporated with the rest. When used the cement, or the piece to be cemented must be heated and both be quite dry.


I have made black cement this way for the Etruscan Ware, but it is too soft. I am inclined to think with Mr. Dessie that the proportion of wax is rather too great, and also that the powder may in some instances be increased to two parts, especially if it be ground very fine.


Lewis recommends the trail of hard old varnished for gilding upon glass.


Q. Whether the Gildors should have aprons fixed to their breeches, they seem to do their business in a wasteful manner. 


It appears from Chemical experiments that salts upon evaporation short into a great variety of forms and ramifications. 


If the Calx of metals ground fine were to be diluted in various solutions, might not these particles be carried by the salts into many pleasing forms, such as appear upon the Mocoaj and in some Silver oars and pebbles. (Let the salt short a little first, and then dust the powder on)


2. To get samples of all the semi transparent gems and of the coloured and variegated flints and marbles.


Gold looks best upon the raised part of vessels, and so will silver, but enamel colours appear best upon a flat ground. 


This sentiment admits of exceptions. 


Would it not answer to wash over all the Slip for fine ware?


Experiment 6th No.1 Powdered Etruscan.

Experiment 7th No.2 N1 and MW.3 equal parts

Both flux well, the first a middling, the second, a good black. This may save the trouble of preparing 903




Upon further examination I question whether No.1 is not as deep as black as 2 though it does not seem to have fluxed quite so well.



November 29th 1768


Have received two specimens of Oil Varnish from Mr. Turner which I wrote for to try them for Gilding.


One Phial is marked No.2. An Oil Varnish for Outdoor Work.


The other . . . A 10 . . .  Mr Turners instructions are that if they are too thick they may thinned by oil of turpentine. If they dry too quick a drop of Linseed will remedy that inconvenience.


Experiment 8. Painted a cup with black enamel in Extravaganza, to be put into the glass oven.


Might not handsome handles be made to something in moulds taken from sticks of rough coral? And good friezes from Brain Stones and Corolines?


To lay leaf - Silver upon Glass, see L'Art de la Veninex [?Voninex Veninec?] P 342 


To gild glass in a manner that will penetrate see L'Art of P 343 Article 20 & 2


I sent to Newcastle the other day for some Kings Yellow, to use it instead of Vermillion in the Gold Size, and I think the Vermillion injures the colour of the gold, but they had none and sent one Naples Yellow instead of it.


With this Naples Yellow I shall make some trials upon the Etruscan Ware for an orange colour etc etc.


The longer time pieces are thrown before they are turned (provided they are kept in good order) the better they work upon the lathe. So say the turners.


When we have a very fine form it seems necessary to keep a pattern of it, as there is often as much trouble and loss of time in making it over again as there was in contriving it at first, and some part or lines are frequently forgot.


A great many vases came out of the oven yesterday morning in a bad condition, some broken and many cracked especially in the Ornaments going in too soft accounts for the destruction of some of the blue sprinkled ones. But whether




being finished in a bad tempura or too hasty firing, or both are the causes of the fractures in the black vases) the men are not agreed. Though as many other things were cracked, it is most probable this mischief chiefly arose from hasty firing. Q further.


Blue Enamel


See Le'Art de la Venini P207,208,209


To try Manganese in the Glaze . . .  fa Milk White.


See L'Art V P 204


To try a little N.Y. in the Glaze to discharge the greenishness that sometimes affects it.


Doctor Henrys experiment to trace the progress of incubation furnishes a good hint for such of our experiments as depend upon being a proper time in the fire.


Experiment 9. Gold laid upon a cup with varnish (My No.4 No.2) diluted with a little turpentine and coloured with vermillion has stood the strongest heat of the stove, not to be dried, and seems to lie on very smooth and adhere very firmly to the glaze. This cup is No.3 the Gold may be scraped off with a knife but does not seem at all affected by washing scrubbing hard with leather in very hot water.


I find a great deal depends upon laying the Size on very thin and even, the common Size stands much better when it is laid on thin and exposed to a stronger heat, but when it is laid on thick, and exposed to a strong heat, it blisters.


December 1st.


Have seen the black clay that was washed over thrown into 6 & 4 and seven small ones in all 17 vases, egg, Aeron, and Pear and Cone pointed forms and have had a chandelier vase thrown in White, after the idea of the metal




vase candlestick sent down by Mr.W [Josiah Wedgewood?].


This White clay is much tougher and more manageable in the Throwers hands than the black. 


It would be very convenient if practicable to have a table calculated to show how much each kind of clay will run in, in the firing.  I.M.


Double bellied vases should be ornamented at the bottom with leaves that are not quite so high as the widest part of the first swell.


Experiment 10. J.B. painted a black vase with N.Y. (Which I shall call Vehicle Turpentine No.3) in Husk Festoons and put it in the glass oven.



December 2nd.


The cup painted with black enamel in extra a. upon the glaze is come out of the gloss oven this morning, it has grounded well, and is quite fine and smooth where it has had fire enough, but the parts where the colour was laid on thick are short, as all the next of the Ware is from the oven.



I will melt the black cement over again and make it more conformable to Knuchles recipe, the proportion and then will stand thus.

Bees Wax . . 2

Resin . . 1

Brimstone . . 1

Powder . . 3


These proportions are much the better than the first and seem to ans very well. The powder should not be ground extremely fine.


This is harder than the Com Stakeanys [?] Cement.


The mixture should be well kneaded in warm water and made up into convenient roles about the thickness of sealing wax.


Almost all yesterday taken up with making a vase candlestick after the idea, but not at all like the Pattern of that sent down by Mr.W [Josiah Wedgwood?].  It was finished last night and is my first composition in Potmaking for the 17 black ones are not turned yet. The snake round the base is not gracefully bended. That part must be improved.




Black Cement


The above cement made a second time according to the above receipt with coarser powder was not so black and not quite so hard. I have ordered and Oz of powder and a little Manganese to be added.

Thus then it stands 

Beeswax 2

Brimstone 1

Resin 1

Powder 4 and Manganese very little (half a part) half an oz.

Hard and good colour. 



Experiment 11. Two tea cups were gilt yesterday with M T s & A.10. One of them was exposed 4 hours to the common heat upon the plate in the stove. The other to a red heat at the bottom of the stove for the same space of time. The second stood almost as well as the first. I think the surface is not quite so smooth. But I fancy this gilding may be very much improved by laying it on where it can be done without any colour, and where a colour is necessary with some substance that will not be liable, as I think the Vermillion is, to grow rough or lumpy in the Fire, it should be some colour that would either flux easily or burn away. (N.Y. or Arnatto)


A cup gilt with the common size and exposed to the same red heat as the above, blistered. (James says) in a quarter of an hour. This varnish therefore is a much better and stronger size, than that, that is now used, and A.10 though not so fine may do for common use as well as the white V.N.2.


December 4th.


To try 10.A.10 with some Etruscan Powder for a cement that will stand the gilders fire. 


Experiment 12. Put some gum Arabick and Borax in water last night and set them in a glass by the fire all night, about half the gum and very little of the borax are dissolved. The solution is soapy. Neumann says borax takes 30 times it own weight of water, or more to dissolve it.




It makes the colour of gold that is fluxed with it, pale, but this may be prevented by the addition of a little Nitris or Salammoniac.


Good Cimabar or Vermilion will totally evaporate in the fire, but it is often adulterated.      Neumanns Ms.


To try whether milk in which quick lyme has been extinguished will not prove a thin cement for the surface of porous vessels? Lime grows hard with blood or gum in a mucilage. Coarse powders of stoney or gravelly bodies with Lime will make a hard concrete, but sand or flints in fine powder don't seem to make it harder than by itself.             Lewis.


Powders for cements in general, I think should not be ground very fine. I suspected before that my Etruscan Powder was ground too fine for the black cement and have some to add not quite so fine.



Colouring of Crystal


See the Article Crystal in Newman Page 7 and Neri Minet, & Knuckel P.166 

Here is a fine field for Experiments.

Salt, sulphur, Sal Ammoniac, Pyrites Pounded, all the metals in small particles mixed with any of the above substances as may probably be rendered volatile, and applied to glaze the surface of vessels with every possible variety of colours.


Gums are mediums of union between water and the resins. Sal ammoniac makes most of the metals volatily especially Regulus of Antimony.


Experiment 10 continued.              Dec 5th. 


The black vase painted with No.3 is come out, the colour stands the fire perfectly but does not at all, or but very slightly, adhere to the ground, evidently for want of a flux.


Experiment 13. White Slip and No.3 ground together to paint Etruscan painted the lip part of a vase. 




Experiment 14. Solution of 8 and 7 which has stood by the fire 2 nights and not half No.8 has dissolved, to be mixed with a little turpentine. If necessary to lay on gold (done without turpentine)


Experiment 15. The same solution with No.3 to paint upon Etruscan (painted the foot with it)


Experiment 16. The same done to lay gold on with - done - 


Experiment 10. Continued. Have put the Vase Exto into a Glazed Sagger and placed it near the bottom of the Glass Oven, and have set in 13 and 15 upon a  vase in a dry sagger



Experiment 14. The gold laid on with this solution was exposed to the red heat in the stove about 8 hours, it does not penetrate at all, and adheres to the glaze very slightly. Experiment 16 exposed in the same manner has lost a great deal of the gold, what remains adheres but slightly, the same particles seem inclining to flux. They shall both go into the glass oven. Washed some of the gilded part over again with the solutions 7 and 8.

These experiments should be repeated different ways as Knuckel says this gold will never come off and that this is one of the best ways to gilding glass.


Experiment 10 Continued. The festoon is now fixed perfectly in the ground, but instead of yellow a deeper black than the body, so that it seems a sort of Damask work. The vase was a bad colour and is now a fine Etruscan black.


No.13, & 15 Continued. No.13 and 15 have both grounded, the slip perfectly smooth, the solution fast but rough, the first is a yellowish white, the other a greenish yellow. This vase has been in a dry sagger, if it had been in a glazed one I suppose the painting would have been black as in the other No.3 the background is much finer.




Etruscan vases wet with drops of rain before they went into the biscuit oven shew them when they came out as plain as when they went in and even after they have been twice in the glass oven the marks are still very apparent.


The pedestals of the Etruscan Vases are not uniform for vases of the same size and are not enlarged in proportion to the size of the vase. These for the larger vases are generally much too slender.


To take away the yellow or green tinges of glass try firstly Nitre. 2nd Manganese Handmaid Val & P276

See also Page 254.


To paint with Zaffer in a solution of Borax upon the biscuit and to glaze over it. 


Experiment 17. - December 8th 1768


Rock shale smooth and fine of the colour of common writing slate from the tunnel at Harecastle is very like Stourbridge clay, famous for glass house pots, but finer in its grain. I mean the specimen I brought last week from Harecastle is finer. There is great plenty of a coarser grain and of various degrees of coarseness, till it comes to a hard sandy gritty stone, which does not seem to fall in the Air into shivers as all the fine very soon does though it all appears hard and solid when it comes out of the ground. This fine sort does not turn into the appearance of clay or shew any tenacious duality till it has been well ground with water, and then it comes to a pretty still lead coloured clay, and with work upon the wheel. Of this I have ordered a cup to be made without any mixture which is now in the biscuit oven.  


December 9th

 Experiment 18. Mr Henshall brought me a specimen of clay full of small shells from Hornington Mare, where they have cut through it, it lies in a bed of 12 or 13 inches thick. This clay is a lightish brown colour interspersed with vegetable fibres, half rotten and has a fine sandy appearance, the shells are very tender and, of a greenish pale colour of this form V  O  And in general about this size.  Made into a cake turns into a crumbly substance of the nature of lime. Might be a good manure.


Experiment 14 & 16. When these came out of the glass oven the gold was all gone and had left only a brownish stain. This oven is too hot for the purpose.




Experiment 19. Gilded a glass the day before yesterday with varnish No.5 and with the solution 7 and 8. Exposed it to the greatest heat of the stove about 8 hours. The gold laid on with No.5 was firm and in good condition, but projected evidently above the surface of the glass and the parts covered with it was opake, but the gold laid on with the solution did not sensibly project as it had penetrated the surface of the vessel, and in some places was evidently smooth as any other part of the glass. The part covered was in general transparent and the particles of gold too distant from each other for perfect gilding. This course of experiment must be pursued.


The  Countess of Stamford is very desirous of having a border or edging of fine dark blue run around the cream coloured plates and dishes and her Ladyship is so very obliging and attentive to the improvements of the manufacture that I should wish very much to gratify her taste in this particular.


I find it is the opinion here, founded upon experiments that Zaffre does not agree with the glaze, that the cerise in the glaze kills it and that it turns out grey and spotted, but not a clear blue.


I understand also that the blue which I have seen very fine upon white stoneware (and which is glazed with sea salt, is laid on in a glaze of flint and lead the same as this, and that the fumes of the salt somehow counteract the effects of the lead.

I learn hereby that Zaffer will stand a very great heat, so that with a proper medium of flux, there is no danger of its flying off in the fires.


With these data let us proceed to experiment observing first however that Zaffre is Collouring earth or regular of cobalt mixed with 2 thirds or more of calcined flint or quartz. And Smalt is a powdered glass made of these substances with the addition of a certain quantity of PotAsh. Metalic substances in general can not be vitrified or combined with vitreous matters, till they are deprived of their metallic force and changed into calxes, Most metals are in their ores in the state of a calx. Regulus of Cobalt both in its Metalic form and in that of a Calx dissolves readily in Aqua ffortis into a red liquor. Thus after strong calcenation we may pretty certainly discover this Regulus in whatever Ore it may happen




to be mixed. This same metal is precipitated from acids Zink not by Iron. Lavis Possin


To paint the edges of two plates one in biscuit the other glazed with the following compositions. 


Experiment 20. Painted the first space with No.6

Experiment 21 3 parts No.6 and 1 No.1

Experiment 22. 4 parts No.6 and 1 of 1.

Experiment 23. 4 parts No.6 and 1 of 9.

Experiment 24. 3 parts No.6 and 1 of 9.

Experiment 25. 5 parts No.6 and 1 of 9.

Experiment 26. 10 only

Experiment 27 No.2 @ 11 equal parts to be used with water.

Experiment 28. Four parts of this mixture 27 @ 1 of 9.

Experiment 29. Four of 2 and one of tin.

Experiment 30. Five of two and 1 of tin. 

These were none of them clear uniform colours though several of them seemed to deserve repetition. 


December 12. 1768


Experiment 17 continued. This cup made of Rock Shale without mixture was set about the middle of the Biscuit Oven. It stands this fire perfectly and seems to be short fired, as it has a good deal of suction when applied to the tongue, it is of a very fine smooth surface, and of a pale red colour inclining to pink. All this shale therefore, which has never yet been applied to any use is a fine clay, and probably good Fire Clay. This experiment must be pursued.


Have painted the top of the cup with 10 and the bottom with our black enamel and order it to be put about the middle of the Glass Oven.  December 13.


The Colour 10 and the black enamel both stand, the Enamel rises above the surface and does not flux at all. No.10 has fluxed and shows that shining appearance which black lead has, and seems perfectly like the black wash of the ancient Etruscan vases which his Grace the Duke of Northumberland shewed us at Northumberland House, and this Cup is so like the Ground only finer, that with these two materials only we may make perfect Etruscan vases.





Large vessels ought to stand a fortnight or three weeks after they are finished before they go into the Biscuit Oven, which will make them much less liable to crack with the application of fire.


February 6. 1796. February 7th.


To dip the Etruscans

                                        Lb  Oz

Experiment 31.   Fine slip 1lb 3oz   No.3  ½oz

Experiment 32.   Fine slip 1lb 3oz   No.3  1oz

Experiment 33.   Fine slip 1lb 3oz   No.3  1½oz 

Experiment 34.   Fine slip 1lb 3oz   No.3  2ozs


Repeated these experiments twice, they are free from white scurf, but rather of an indigo cast 31 is the smoothest, 32 and 33 nearly of the same smoothness but not equal to 31. 34 very rough, but a good colour.



For Onyx Ground and for a White Colour.


March 15. 1769.


Cream                                 Pint

Experiment 35 White Slips 1 pint  No.10  1 dr

Experiment 36 White Slips 1 pint  No.10  2 dr

Experiment 37 White Slips 1 pint  No.10  3 dr

Experiment 38 White Slips 1 pint  No.10  4 dr

Experiment 39 White Slips 1 pint  No.10  5 dr


Experiment 51 White Slips 1 pint  No.10  16 dr


White Ore - Weight 2 Oz



Roasted in a covered crucible in a gentle fire gradually till the vessel is almost red hot, keep it in this state a few minutes, then take of the Tile, and the Ore shall be changed from a black to a yellowish or Ash Colour, beat this roasted Ore to a fine Powder and add twice its quantity of black flux and ½ Oz of Iron filings not rusty. ½ Oz Glass Gall beat them altogether in a Mortar till well mixt.


PAGE 15 


and put them in a crucible that will hold two or three times as much. Then cover them over ¼ inch with Common Salt and press them with a finger, shut the Crucible with a Tyle or another Crucible well luted, then dry the whole at a moderate heat, put the Crucible in a Wind Furnace heap it up with Coals covered two or three inches, keep up the fire increasing gently till you hear the salt crackle, and a gentle hissing, keep up that heat till the hissing is over, then increase the fire suddenly till the whole mass is melted which will be done in a ¼ of an hour in a moderate fire, strike it two or three times gently with a Hammer when you set it on the floor and not open it till cold.



Friday 30th July 1773 (crossed out)


Common Materials used in Pottery.


All the materials used in the Pottery are doubtless the productions of the Mineral Kingdom. That Art converts clay stones and metals into useful and ornamental Vessels, into Pictures, Busts and Statues which differ from each other infinitely. Velvet, plain silks, brocades etc are all made from one single production of a worm, and a plain silk stocking and a ribbed one are all the same materials, and yet even the small difference of a peculiar kind of Rib having produced a valuable manufactury has been deemed sufficient ground for a Patent, and its validity has been established in the Courts.

Caylus Vol 1 P00 Speaking of the great beauty and perfection of the Etruscan Vases concludes that, "The Etruscans could not have produced so many inimitable pieces without a perfect knowledge of the Art joined to the neat happy natural talents, as all that has come out of their hands has an Original Character, which can not be confounded with any other.




 In a mechanical discovery, such as that in the Stocking Frame which made a sort of Stockings called turned Ribs, on what did the invention consist? Not in producing any new materials or mechanical principles, but in such a new combination of the mechanical powers as enabled that machine produce and new Effect. A Rib in a Stocking which produced a new Article of Commerce very much sought after and therefore a new and valuable trade to the Nation. [this reference to a machine that produces stockings is possibly a reference to a devise made by Thomas Stamford, father in law of James Caldwell]


For the same manner if we are asked wherein cannot invention of our encaustic Painting of Etruscan Vases, we say not in the discovery of any new chemical Principles, or materials, but in such a new Combination of Chemical Materials, and Principles, as has enabled us to produce a new Effect, Amarmor and Style of Encaustic Painting, totally new in the  Kingdom, free from the Glossy appearance of modern Enamel; resembling the curious painting upon the ancient Etruscan Vases, which is very much sought after by Antiquarians and Connoisseurs and which has produced a new and valuable Article of Trade to this Nation.



Put Gold in Leaves into Spirit of Sea Salt


Pour Spirits of Nitre in gently till the Mixture apparently works upon the Gold, let this stand till the mixture is saturated with the Gold. In this solution there will generally appear some silver which will fade in a yellowish Powder to the bottom of the Bottle. This Silver will be of no disservice to the Purple, if it has any Effect it must be to make the Purple more red.


Make a solution of Tin in Aqua Regia, dilute this with a large quantity of Water, take a Bason of Spring Water, pour into some of this solution of Tin and then some of the Gold till you find a precipitate of a clear purple colour.




3.      1 Chrystal

         3 Lead

        1/8 Nitre

         ¼ Calcined Borax



Earth from John Walsh Esq - of a beautiful grey colour with a blue effervescence upon some parts of it. This earth is light and friable, it ferments strongly with Spirit of Nitre. Being exposed in an Enamel Furnace for nine hours, 3 ounces or 60 penny worth - when calcined (the remainder being evidently a Calx of Iron) weighed only 33 penny worth.


This Calx used as an Enamel colour with a proper Flux, gives a brown reddish colour like other Calxes of Iron.


From the great proportion of Iron in this earth together with the Alcaline nature of the earth itself I am of opinion it ought to be tried as a cement or XXX which we purchase at a Great Expence annually from Germany.



Littiarge 3 parts

Calcined Flint 1 part


Pound and mix them well together and run them into a yellow glass. Pound this glass and grind it into a subtle powder, moisten this well with a salinated solution of silver, and make it into a paste which put into a crucible and cover it give it at first a gentle degree of fire, then increase it and continue it till you have a glass which will be green. Pound this glass again and grind it to a fine powder, moisturing this powder with Beer, so that you may apply it to the Earthern Ware, let the vessels be first well heated; then put under a muffle, and as soon as the glass runs you must smoke them and take out the vessels.



1 oz Enamel

1/6 Ground cream Biscuit

1/32 Cherokee Clay calcined and ground fine.


The above white is very good especially upon an Ivory Ground, and it seems to me that our best Ground for Painting will be made with this colour upon our Ivory Plates, laid and fired several times over as the fine Enamel blues and other colours at Seve.




1 Borax

1 Flint

Flux calcined together.


One part Flux measured and 1 Ground Manganese.

Dead colour first with gold Size and black faintly, drig it well then lay it over with black in Turpentine, as smooth as possible.


Fired in the Enamel Kiln and succeeded well for an Etruscan Black upon Cream colour by which means much lighter vessels may be made than in the black Porcelain, and this ground takes the red border as well as the Porcelain Ground



Experiments to be made.


1. 2 parts of Iron filings

    1 part of Flowers of Zinc (Lune Philosophica) calcined together in a crucible 4 hours. Give a more perfect Calx of Iron, than can be procured without the Aid of the Fire in many days.   Sage Vol 2. P.111


Perhaps this may give some Peculiar colour in Enamel. 


2. Try Copper in the same way



3. Compound of Tin, Cobalt, and Marine acid. Try these for a Purple. Take Zinke Cobalt Sea Salt equal parts. White Glass or Enamel.


4. Dissolve Iron in the Phospheric Acid.


5. Dissolve filings of Iron in weak Aquafortes, pour into this a solution of Salt of Tartar, and you will have a greenish blue precipitate which when well dried will become brown and be 88 lb p Ct heavier than the Iron made use of. This Precipitate is indissoluble in water like Prussian blue. And Mr Sage says is a Salt formed by the Phosphoric Acid & Iron. Try this for an Enamel Colour.




6. Iron gains extremely in weight by calcinations even 42 lb per Ch in 60 hours. Try if Calx of Iron severbrated a long time is more fixed as a Colour.


Ex 49    2 parts Fluor

             2 parts C.C.

             1 part Quicklime

This vitrifies in a very strong heat.


Experiment 50.   2 parts C.C.

             4 parts Fluor

             2 parts Nitre

             1 part Lime

The ffluor does not appear to vitrify with the Nitre.


Experiment 51 The above with Pot Ash instead of Nitre.


Experiment 52 Spanish Barilla instead of the other salts.


Experiment 53 12 parts Fluor

             6 parts Quick Lime


             1 part Borax

Very hard and does not vitrify perfectly.


Experiment 54  2 parts P Stones

            2 parts Quick Lime

            1 part Nitre


Experiment 55  12 parts Fluor

            6 parts Ch clay

            2 parts quick lime

            1 part Borax


Experiment 57   12 parts Fluor

            6 parts Ch Clay

            2 parts Quick Lime





Rock Chrystal




Cherokee Clay


Peculiarly favourable to purple and other fine colours. But clay stops vitrification too suddenly and is apt to leave a body not so hard as it ought to be in the fires we use.



General Flux          May 12, 1772

1 Ground Crystal

1 Calcium Borax


Experiment. A cup cream Coloured to be turned into Etruscan on the outside, lay it over with gold Size, on this put a little colour, then paint it over very even with the Brush.


The Colour -  

2 parts ground Magnus

1 part Flux 


The Flux -

1 part fine calcined Flint

1 part calcined Borax


It was fired in a crucible and broke with taking it out, the Colour was grounded well, a little shining, but not equally so. It was not uniform black, but grayish and flecked, it seems to be short of Colour. Mr Rhodes thinks had too intense a Fire. The pieces are marked No.100.

[James Caldwell's notebook on experiments ends here]



PAGE 1 New Book


A Catalogue of Fossils [Clays]






1 Earths

2 Sands

3 Stones

4 Salts

5 Pyrites

6 Semi Metals

7 Metals

8 Inflamables

9 Extraneous Fossils




Earths - Class 1st


No. 1  Pipe Clay. From Poole in Dorsetshire, Biddleford in Devonshire and other places, used for making pipes and with Flint, for Flint Ware.

Queens ware etc. It is of a light grey colour and does not ferment with acids.


No. 2  Fire Clay. Of a whitish colour from Dr Borlases estate in Geid near the Lands End, Cornwall, sent to Wales, Bristol and other places for making fire Bricks. It does not ferment with acids. This and many other Cornish fossils were collected and given me by Mr Wedgwood in 1775 when he went to Cornwall on account of the Moon Stone or Growan Stone, and Growan Clay.


No. 3  - Growan Clay. From Guenap [Gwenapp?] near Redruth, Cornwall (Mr. Grenvilles Estates) called by the Miners Priam. It accompanies the loads of tin and lies in veins from 2 to 6 inches thick, it is finer than the common Growan Clays, has less Stone in, it of a White Colour and friable. 




No. 4  Growan Clay. From Trelhewys [Trethewey's] Farm near St. Stevens [St Stephen's], not far from Saint Austle,, in Cornwall, some of the first clay engaged by Mr Wedgwood and Mr Turner for the Pottery in Staffordshire. Their clay is of a White Colour with shining particles and small lumps of white granite in it. It does not ferment with acids and is supposed to be the Kaelin of the Chinese. It is evidently the Moon Stone or white Granule in a decomposed state.


No. 5  Growan Clay from Mr Pitts Estate near Saint Stevens, Cornwall, a fine friable white clay with little stone and few micae in it, being more perfectly decomposed than some other specimens of this kind and much resembling the Priam. This clay and the Stone No&ldots; Class have been the object of a Patent granted in the year 1758 to Mr Corkworthy of Plymouth for the sole right of making them into Porcelain equal to the Asiatic.

See the History of an Application to Parliament for the Extension of the above Patent in a Collection of Papers published upon this subject.


No. 6  Growan Clay - from Guinap in Cornwall, got 6 fathom deep, thickness of the bed unknown. It is of a White Colour mixed with Micz and Stone and does not ferment with acids.




No. 7  Growan Clay. From Tregon in Hill in Lord Godolphins Estate. Of a White Colour, friable in the fingers with stone or Mics and does not ferment with acids. These clays with little stone or Micz in seem to be more perfect decompositions of the Moon Stone than the others and to be more perfect clays.


No. 8  Soap Rock, or Steatites from the cliff at the Lizard Point, Cornwall in the Estate of Mr. Tonnereau (Fonnereau ?). It is pretty hard and solid of a whitish colour streaked or intermixed with bluish and greenish veins, the surface is slippy to the touch. It does not ferment with acids. This is used for making Porcelain at Worcesters and other places.


No. 9  Indurated Steatites from the Lizard Point. This specimen is very hard, it is of various colours running in veins and seems to be approaching to the nature of Jasper. It does not ferment with acids. There are vast quantities of this matter to be found near the Lizard and various colours, and of all degrees of Induration. It would be proper to examine this Country for Quarries of Jasper.


No. 10  A Greyish Earth, or clay covered over or mixed with a Blue powder. Found in a bed amongst the coal strata at Golden Hill in Staffordshire. See Experiment Book, Page 77.


No. 11  A White and very hard indurated clay approaching to the nature of Jasper with an undulated or fluted surface covered over with a beautiful white enamel, the inside being less white and without any mixture or shining particles. It does not ferment with Spirit of Nitre. This fine specimen was sent to me by Mr Friezse jun from Cornwall. See Experiment Book Page 80.




No. 12  Red Earth from the Masketo Shore. Experiment Book 77.


No. 13  Orange coloured Ochre extremely light from a lead mine near Matlock, Derbyshire. Experiment Book P.73.


No. 14  An extremely Light Olive coloured earth with streaks of yellow in it, and no grid. Absorbs Aqua Fortei but does not ferment with it, is of impalpable finess, stains the fingers of a reddish brown colour. It stains paper, is a good brown paint for watercolours and gives a peculiar brown in Enamel. Experiment Book P 71 Sec 2d


No. 15  Black earth from Clappergate in near the old Bloomery, sent to me by Mr Knott, January 6, 1775. It gives a purplish colour in Enamel like Manganese but seems to be Iron XXX decomposing. The above colour was made with Nitre and Borax. With the Lead Flux it gives a good brown and appears to be Iron decomposing.


No. 16  Fine white clay with spangles of Talk from Ayoree in the Country of the Cherokees in North America. Mr Wedgwood was at the expence of sending to the Cherokee Country for this clay and procured 10 or 12 tones of it.





Sands - Class 2nd


No. 1  White Sand. From the Isle of Wight. I visited the pit from whence this sand is dug in June 1771 in company with Mr Wedgwood and Mr Moore, Secretary to  the Society of Art Manufactures and Commerce. It lies near the seaside in Alum Bay under a high beach of clay and Alum Shales. The stratum is nearly upon the level of the sea and has no dip. It is from 20 to 30 feet thick, the property of Mr Ussy of Fresh Water who sells it at 10 /per ton upon the spot. This is a very fine sand and used for making glass. Bristol takes 200 to 100 tons a year and Liverpool a small quantity once in 2 or 3 years.


No. 2  Palant Sand from Saint Ives Bay in Cornwall. This sand is of a Snuff colour and should be examined. IT gives little or no colour in Enamel.


No. 3  Black Sand from Lake Champlain from Mr Bakers Catalogue, given me by my good friend Mr Wedgwood who purchased about 1/3 of Mr Bakers valuable collection, and I am obliged to Mr W for all the samples from that collection.


No. 4  Black Chocolate coloured sand mixed. Bakers catalogue gives a rich brown colour in Enamel and is evidently an Iron sand.



No. 5  Black Sand - from Mr Bakers Catalogue.


No.6  Yellow Sand - from ditto.




No. 7  Black and chocolate grained sand from Egmore near Walsingham. Bakers Catalogue. Resembles No. 4


No. 8  Fine shining Black Sand - Mr Bakers Catalogue.


No. 9  Black Sand taken out of a stratum in a gravel pit on Moushold Heath 10 yards from the surface. Baker. Q. Where is Moushold Heath?


No. 10  A Black powdery matter like Iron Schles. Mr Baker had written upon a paper with this sample. County of Wicklow in Ireland. Q What is it?


No. 11  Deep Chocolate coloured sand. Baker from Norfolk. 


No. 12  Sand of deep red colours. Baker. 





Stones - Class 3


1. Argillaceous. Or Compounds with clay.


2. Caleauous.


3. Gypseous


4. Fluors


5. Nitrescent Stones


Class 3 Sec 2.


Calcarious Stones


No.1  Stone from Bath in Somersetshire called Bath Free Stone collected by myself, June 7th 1775. That day I examined the quarries near Prior Park, which are worked in sheets about 30 feet deep at which depth the best stone is to be found. All above is rubble or shievery stone, of the same nature as that below. The joints are from 2 to 3 or 4 feet thick and 3 or 4 feet long. The pieces lie upon one another as if they were stones laid without mortar in a wall. They come to a harder stone below which they do not get. There are many quarries now open. The works under ground are very


extensive. The roof, full of jonity broken stones, that seem ready to fall upon ones head, is supported by pillars left in the quarry that form a sort of groined arches. This stone is composed of round small particles like millet seeds, or Ova of Fishes. It is soft and of a yellowish colour, when moist and first got, and becomes whiter and harder when it has been exposed some time to the air. The globular seeds or ova are hollow and when cut present little hollow hemispheres, in many of which - perhaps in all, there is another little globe or nucleus and these spheres are cemented together by a tender mud, without shining particles or the least appearance of sand. The whole fermenting strongly with Spirit of Nitre. Of this stone, almost all the houses of Bath and the neighbourhood are built and being very soft and easy to cut in all directions, vases and architectural ornaments are made of it, at a very moderate expense. In the fissures of this stone there are frequently stalactical chrystalizations as in one of the specimens of this number.


No.2  The same kind of Stone mixed with flinty pebbles taken up by myself in a quarry by the roadside between Bristol and Gromy about two miles from Bath. This likewise ferments with Spirit of Nitre.


No. 3  A smooth Whitish Stone of invisible particles from a wall by the Upper Road between Bath and Bristol, about two miles from Bath where the roads divide, and the lower branch leads to the new bridge. It was got from a quarry just by, now filled up (June 8, 1775) and ferments with Spirit of Nitre. It appears to be an indurated calcarious mud or clay. This specimen mislaid.




No.4  Hard bluish Sume Stone                June 8 1775

About half a mile from Bath, turning to the right a little way out of the upper road towards Weston, I saw a lime kiln and just above it Large Stone Quarries of which stone this is a specimen. The quarries are large and worked open to the day. The beds consist, just a rubble, or broken lime stones intermixed with clay, below this there are 10 or 12 strata of lime stone from 1 to 2 or 3 feet thick divided by seams of clay 6 inches to a foot thick. In this limestone are found many petrified shells, vertebrae of large fishes, jaws of fishes, fishes teeth, and particular nautili, and Cornua Amonis from a few inches to 2 feet diameter, corresponding exactly with the engravings in Hooke's Posthumous Works. Specimens of which I have procured, and shall mention in the Class of Extraneous Fossills. The strata in these quarries seem to lie quite parallel to the horizon, but the workmen told me they dip gently towards the River Avon, about 30 feet above which, and at a quarter of a mile distance, the petrifications are found. The petrifications are not found upon one layer only but in all the strata indiscriminately, above one another, as well as in the seams of clay that divide them.


No.5  Ketton Stone. A whitish or light brown stone from Ketton in Rutlandshire, where there are large quarries of it. It consists, like the Bath Stone of round globules like fishes roe or Millet seeds. The Ova are rather larger than those of the Bath Stone, and somewhat more distinct, being united together almost without any visible cement. It is used for building and ferments with Spirit of Nitre.


No. 6  Portland Stone. Of a whitish colour and of a powdery texture without sand but rather consisting of very small ova, and a calcarious mud in which there are many sea shells harder and more durable than the body of the stone, as may be seen on the surface of old walls, built with this stone, and which I have particularly observed upon the balustrades of the Top of Whitehall. It is an admirable free stone, and ferments with Spirits of Nitre.            Portland in Dorsetshire.




No. 7  A Soft Calcarious Stone

A soft calcarious stone or slate with a curious undulated and embossed surface many perforations. This was given me by Mr Gwynne [Guynne?] of Brecknockshire under the title of Petrified Clay from the neighborhood of Brecknock in South Wales.  It is from the banks of a river where the material lies in great quantities, the river runs amongst mountains of lime stone and this stone ferments strongly with Spirit of Nitre, it may be a very valuable material as a Marle or for smelting Iron.


No. 8  Purbeck Stone. A hard grey stone of a scaly texture without sand or ova, from the Peninsula of Purbeck in Dorsetshire. It ferments with Spirit of Nitre, and is much used for Hearth Stones etc.


No. 9  Hopton Stones. A hard grey stone of a scaly texture with shells in not much unlike the Purbeck Stone from a quarry near Middleton, out of the road between Hopton and Matlock in Derbyshire. It ferments with Spirit of Nitre and is much used in Derbyshire for common chimney pieces, hearths, floors etc, but is extremely apt to stain with grease etc.


[The note books entries end here.  The index at the beginning indicates that James Caldwell intended to add further notes however it would appear that he did not do so.]


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