What is Gilder's Chalk?

[AzoMittle]

In one of Faber's violet star formulas he lists gilder's chalk. I tried googling for it and got several contradictory results; I couldn't find any exact results for gilder's chalk but I did find French Chalk used for gilding as well as some other chalks related to gilding. I found French Chalk listed as talcum powder (H₂Mg₃(SiO₃)₄), Gilder's Refined Whiting as Calcium Carbonate, and Italian Gesso as calcium sulfate dihydrate (CaSO₄·2H₂O).

 

Can anyone confirm if any of these are the correct substance, or what it actually is? Because these are obviously very different compounds with very different effects.

 

For reference the formula is:

 

20....Potassium Chlorate

07....Shellac

04....Gilder's Chalk

01....Paris Green

01....Calomel

[Davidg1]

AFAIK It is French chalk AKA Talcum powder.

[lloyd]

I've looked back at some formula references dating back prior to the 1930s. In five of the seven I looked at, Gilders' Chalk was specifically mentioned, and described as being a particularly pure form of "whiting" (calcium carbonate), but in fairly coarse particle sizes.

 

One of the remaining two did not mention it, and the other mentioned but never defined it.

 

In those coarser grades mentioned, it was deemed suitable for making "putty" (oil [often boiled linseed] and whiting actually ground IN the oil) for glazing and for smoothing contours on objects that were to be gilt with gold leaf.

 

Gold leaf is particularly thin and delicate, and thus subject to easy puncture. Smoothing a surface so there are no sharp declivities helps prevent punctures as the leaf is pounced with gilding brushes.

 

Here's one such reference that is on-line, and thus accessible (the scan is pretty bad, though):

(excerpt) from The Kentucky Geological Survey of 1913, found at: https://archive.org/stream/reports00geolgoog/reports00geolgoog_djvu.txt

 

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*584 First Annual Report Uses and Technology. The uses of calcite depend on the following: 1. Its white-color and body: for water paints, cal- .cimine and white wash ; wall paper prints ; putty ; modi- fication of the shade of other pigments; crayons; tooth .powder; polishing powder for glass and metal; filler for rubber; paint for insulated wire. 2. Its neutralization of acid whereby calcium ace- tate, sulphate, etc., are formed : for purification of wood alcohol and petroleum (in all i)aints) ; and for medical purposes. 3. Its chemical composition: for manufacture of lime, carbonate of soda, carbonic acid gas and many other chemical compounds; by potteries. 4. Its formation of silicate: for manufacture of Portland cement; as a basic flux. 5. Its lime content action as cement, and power of moisture absorption: for agricultural lime. For uses under the first and second lieadings finely ground cal(*ite or chalk, having a calcium carbonate con- tent of uj)ward of 95 ])er cent, known imder the name of Whiting, is emi)loyed; this grade is also necessary in the manufacture of carbonic acid gas and certain chemi- cal compounds. For the other purposes, calcite of in- ferior qiudity may be employed, either in lump or gravel form, except in the case of agricultural lime, where a ground product is necessary; for the last purpose, how- ever, the cost of nmnufacture from calcite would exceed what tho product would bring. The lower grades of whiting usually carry about 95 per cent of the calcium carbonate and not much above li per cent of silica. The better grades carrj^ 98 per cent or upward of calcium carbonate. The commercial and gilders whiting, because of their coarseness, mix best with oils and find their chief use in making putty. The better grades are used for paints, rubber filling and carbonic gas manufacture; the finely divided chemical by-j)roduct is also used for these purposes, but it has less body and hence is not as desirable for paints. Marble dust and pure oolitic limestone is little used in this country for w^hiting, the former more than the latter, and Kei^tucky Geological Subvey 585 such as is sold goes chiefly for the manufacture of car- bonic acid gas. Whiting is used as a base for water paints as, for example: '* Marble lime" color for outside work con- sists of cassein soluble in alkali 100 parts; caustic lime for marble 100 parts; Whiting 800 parts; borax one part; ultramarine 2 to 2V2 parts. Calcimine consists •of a mixture of Whiting, glue and water. In making putty, w^hiting is simply ground by means of a putty chaser with oil, either mineral, com, cotton- seed, or raw linseed oil; boiled linseed oil is used when a quick drying putty is desired or litharge or other driers may be added to a raw" linseed oil putty. Jew^eler's putty or putty powder and plaster putty are entirely different products, as is stove putty. Source of Competition, Production, Imports, Etc. Whiting made from calcite must meet the competi- tion of whiting made from the groat chalk beds of the Cretaceous in p]ngland and France and a recently dis- covered chalk deposit of immense size in Mexico; of whiting made from mar])le and pure oolitic limestone; and of tliat obtained artifically as a by product in many chemical processes, for example from the residue of paper pulp. However, the bulk of whiting used is made from slightly impure chalk. Owing to the difference in ocean and inland freights and also the 'difference in first cost of product, Kentucky whiting could not compete with coast whiting except with the higher grades. 

[AzoMittle]

In making putty, w^hiting is simply ground by means of a putty chaser with oil, either mineral, com, cotton- seed, or raw linseed oil; boiled linseed oil is used when a quick drying putty is desired or litharge or other driers may be added to a raw" linseed oil putty.

 

Interesting. If that's what it is supposed to be it makes me wonder if it was supposed to act as a binder (as opposed to how we usually use carbonates for coloring). If it's the talcum powder it seems to be acting as a fuel (which makes sense, 20 parts oxidizer out of 33 total parts gives 60% oxi). Both of those seem reasonable.

 

edit: actually if its the former it would still be acting as a fuel, so that makes even more sense, I think.... maybe....

 

It's time I got some sleep though, I know that for sure.

Edited May 29, 2016 by AzoMittle

[lloyd]

To me, it makes complete sense that the calcium carbonate would be used. It's not a fuel OR an oxidizer... it's a color donor and flame-cooling additive.

 

LLoyd

[AzoMittle]

Doesn't calcium carbonate give an orange color though? This was listed as Violet (it's in Dan Harman's (spelling?) Formulary).

 

Do you think it is being used powdered for the color donor / flame cooling? Or mixed with the oil to make a putty to bind with?

 

Why isn't it considered a fuel or oxidizer? I thought every compound, even if they aren't primarily used as one or the other (for example being used primarily as a flame coolant and color donor like it is here) still had some inherent redox potential value?

Edited May 29, 2016 by AzoMittle

[PhoenixRising]

I'm no mixologist, but looking at some color charts, you can mix Blue (from the paris green) with red or violet and get violet.

 

From what I can gather with my google power, Mercury (from the calomel) should emit most in the violet or green spectrums? Forgive me if I'm wrong.

 

Also, potassium burns with a pale purple too If I'm not mistaken.

[lloyd]

I'm guessing that the distinctly reddish orange of a calcium flame combined with the blue from the Paris Green would result in a violet(ish) flame. The calomel, of course, would provide the necessary chlorine to elicit the colors from their donors. Generally, the mercury from calomel enlarges the flame envelope, but doesn't radically affect the color.

 

A LOT of color names have been 'fudged' over the centuries of pyro, in order to make them sound prettier (or more accurate) than they really are!

 

LLoyd

Edited May 29, 2016 by lloyd

[PhoenixRising]

Just for fun I looked at Veline's purple, and it's 80%Blue, 5%Orange, and 15%Red. I know it's not exactly comparing apples to apples, but it does echo what you just said, Lloyd.

 

Maybe they should have named it "Violet of Mystery" oOooOooh, spooky and obscure!