medieval copper sulphate?

[kate/bob]

I've managed to make a lovely colour of green using weld and copper sulphate. The question is, would a dyer in the late 15th century have had access to copper sulphate? I've tried doing some research, but am a bit stumped not being a chemist.

[Neil of Ormsheim]

Oil of Vitriol (Sulphuric Acid) has been known and used since Roman times. Dissolving metallic copper or black Copper Oxide in Sulphuric Acid will yeild a blue solution. This is Copper Sulphate. Evaporate off the liquid and it will give you nice, pretty, blue crystals of the same - easier to store and transport.

[guthrie]

Yes, they likely would have, but less access the further back you go. It's in the 16th century English lists of customs duties. In there it is called copperas, and the accounts also list green vitriol which was used for ink making, but the problem is that they were often mixed up together and not always distinguished properly.

As for oil of vitriol, Neil, I'm afraid you have likely been misinformed, or else you'll need to tell me your sources because it doesn't fit with what I know. Yes the Romans had vitriols, of various colours, for various uses. But sulphuric acid as a separate substance is more a 16th century thing, with occaisional alchemical productions in the 14/15th centuries and possibly by Arabic alchemists before that.
Therefore nobody, especially not dyers, was dissolving anything in sulphuric acid. Copper sulphate was recognised as coming from Cyprus, being a liquid turned into blue crystals, as you say, but the liquid came from natural action of water on the copper sulphide deposits.

So the real trick would be to see if you can find some dyers accounts or purchases or instruction manuals, especially from the 16th century, and see if they used it at all, and if they didn't, no you probably shouldn't. I'm sure it was in England, but not necessarily in the amounts to be used by dyers, and even if they did it would be expensive so I'd expect some mention of it.

[Medicus Matt]

Yes, they likely would have, but less access the further back you go. It's in the 16th century English lists of customs duties. In there it is called copperas, and the accounts also list green vitriol which was used for ink making, but the problem is that they were often mixed up together and not always distinguished properly.

Are you absolutely certain of that Guthrie?
I thought copperas was copper sulphate but in "Copperas: An account of the Whitstable Works and the first industrial-scale chemical production in England" (Allen, Cotterill and Pile. CAT 2004), Tim Allen is quite definite that it is ferrous sulphate derived from iron pyrites.

[kate/bob]

Thanks guys.

The copper sulphate to weld ratio is very small, so you don't need very much for a lot a very bright green cloth.

The search will go on, now that I know what it is that I'm looking for!

[guthrie]

Yes, they likely would have, but less access the further back you go. It's in the 16th century English lists of customs duties. In there it is called copperas, and the accounts also list green vitriol which was used for ink making, but the problem is that they were often mixed up together and not always distinguished properly.

Are you absolutely certain of that Guthrie?
I thought copperas was copper sulphate but in "Copperas: An account of the Whitstable Works and the first industrial-scale chemical production in England" (Allen, Cotterill and Pile. CAT 2004), Tim Allen is quite definite that it is ferrous sulphate derived from iron pyrites.

I'm absolutely certain that the names and labels were mixed up repeatedly at various times in the last 700 years.
For instance, the 1582 Tudor book of rates distinguishes between copperas, copperas green, copperas white. The green would be iron vitriol, the white some other variety, perhaps zinc, and the ordinary the blue copper. But it is likely that there was some contamination issues with the blue and the green, and distinguishing them would be difficult at the time. Iron sulphate is, when fully hydrated apparently a blue-green, so obviously separating it from the blue would be tricky.
As for the vitriol production in England, that was iron pyrites based, and judging by the book of rates be called copperas, or rather green copperas, but as is usual people connected with it would shorten that to copperas. Yet oddly enough alchemists and people making ink for writing used the term vitriol not copperas, but interestingly enough Biringuccio, plage 98 of the Dover paperback edition, says that "This is thrown forth by the heat like a skin on the mixed ore when it is weathered, This is a very powerful vitriol and it is not called vitriol but copperas."
His book was printed in 1540, so that might explain the increased use of the term copperas. Of course the English production was long after the medieval period although it would be interesting to know if it had any use by dyers. I've got a book somewhere that would likely say but can't recall where. On the other hand, a sulphuric acid containing solution probably wouldn't be very nice for the cloth, because it eats organics, so Kate/ Bob needs to let us know how this cloth fares. Mind you one of the books on dyeing that I have describes such a use of copper sulphate, about half a teaspoon per 100g of wool, so obviously they've not had any problem.
One medieval recipe I've seen for making ink just refers to vitriol, meaning the green stuff. We can be sure it was in the country throughout the high and late medieval period, but as for blue vitriol, that is another matter.

[sally]

Copper acetate may be worth exploring too. You can make that very easily by exposing copper to vinegar fumes in a closed container, and the end result looks very similar to copper sulphate and works pretty much the same way in dyes. I know thats around from the Roman period onwards. Here's some I made for a project on Roman eye medicine:

[John Waller]

Copper acetate may be worth exploring too. You can make that very easily by exposing copper to vinegar fumes in a closed container, and the end result looks very similar to copper sulphate and works pretty much the same way in dyes. I know thats around from the Roman period onwards. Here's some I made for a project on Roman eye medicine:

Copper acetate small.jpg

AKA verdigris.

[Dave B]

Which is certainly used in art pigments, but I thought it wasn't a terribly stable pigment, and had to be varnished over, so I don't know how good it would be for dieing or whether your color would change?

[guthrie]

Which is certainly used in art pigments, but I thought it wasn't a terribly stable pigment, and had to be varnished over, so I don't know how good it would be for dieing or whether your color would change?

Yes, according to Thompson it isn't stable at all, susceptible to water or alkali or others.
However as a dye, you'd be carrying out an actual chemical reaction, so stability is probably less of an issue, that is, if verdigris can actually dye cloth, not seen any reference to it doing so so far.

[Dave B]

A quick google suggests that dying with verdegris prepared from copper plates in vinegar was established in the georgian era, but I didn't see anything earlier:

http://books.google.co.uk/books?id=580GAAAAQAAJ&pg=PA378&lpg=PA378&dq=dyeing+with+verdigris&source=bl&ots=ZVrDiURR1q&sig=mrLLgK_FmdcRj9Yr-uAwt7H1eag&hl=en&sa=X&ei=Kj4EVP2fIYXSaL6MgdgJ&ved=0CGYQ6AEwCA#v=onepage&q=dyeing%20with%20verdigris&f=false

[gregory23b]

copper filings are used to mordant blue dyes, the Strasbourg Manuscript has a blueberry and copper dye recipe for string.

Copperas in the medieval sense is mostly ferrous sulphate or decomposed pyrites if found naturally, yet there are recipes which confuse this with copper.

I have dyed bone with verdigris liquid, easy to make and takes the bone well. It was also used to dye cloth.

Verdigris is soluble in both water and oil, making it very handy for dyeing as above and glazing when dissolved in oil.

Verdigris should not be painted with lead as they react and spoil each other.

[Dave B]

Copperas in the medieval sense is mostly ferrous sulphate or decomposed pyrites if found naturally, yet there are recipes which confuse this with copper.

.

Interesting, as Ferrous sulphate dies things very brown - I know as I've worked with it in the past and inadvertantly dyed my clothes.

[John Waller]

Copperas is most definitely iron or ferrous sulphate. It was a by-product on a chemical plant I worked on making titanium dioxide. Fascinating process - you start with a black sand-like ore and end up with a pure white powder. But I digress. It was in the form of green crystals which is , I suppose, why some people think it contains copper. It don't. Also know as green vitriol IIRC?

[The Iron Dwarf]

Ferrous sulphate ( Copperas ) is also used in refining gold but it only works if fresh, when oxidized it is no good, and there is no copper in it.

copper is also used, both are used to get metals dissolved in acid out of the solution as a precipitate