Colouring glass

Since making my own glass seems very hard to do, I have cheated a bit. With my furnace up around 950 to 1,000 degrees, I can melt normal modern bottle glass. So as a test today I tried to colour some glass, by means of rust.


You see, iron makes glass green in colour. Green glass was produced regularly in England, because they used yellow sand which has a high iron content, as little as 0.5% colouring the glass green. If you wanted really clear glass you had to use white sand or quartz, which were not widely found in the UK, more often found in Germany. However all through the medieval period window glass was imported from the continent.
A somewhat green british glass alembic can be seen here:


(From: http://www.exeter.gov.uk/timetrail/07_middleages/object_detail.asp?photoref=7_89, Exeter during the middle ages)


This is the glass before:

Sitting in a crucible of my own manufacture that has survived at least one firing up to the correct temperature.

So, I melted the glass to a gooey consistency, then dropped some rust on top, and stuck it back in the furnace for ten minutes more. After that time I took it out, partly because I was running out of fuel. The end result was this:



It’s not very exciting, is it? There was not enough time for the iron to diffuse through the glass, and also I had not mixed the metal in properly. Nevertheless a green tint should be visible. This is a fairly simple demonstration that I could carry out at an event without any trouble, especially if I mixed the iron into the glass properly. Moreover, different colours can be had with different additives.

The difficulties of finding original sources (and medieval fire retardant part 3)

Those of you who recall my last experiments making alleged fire retardant will remember that I found information about it in the journal of the Historical Metallurgy society, in an article by Jochem Walters. With regards to the fire retardant he says:
Un-slaked lime has been a component of widely varied fire-proof products throughout the modern period. See the Curioser Kunstler (1 133/257/305/348)

There was an e-mail address at the bottom of the article, so I mailed him a couple of weeks ago, and received a reply.
He said that the Kurioser Kunstler was the largest collection of recipes for all sorts of things, and was published by Johann Kunckel von Loewenstjern, anonymously in Nuremberg in 1696. The full title being „Der Curieusen Kunst- und Werck-Schule
erster und anderer Theil“
Now, Kunst translates roughly as art, and I think a rough translation would read “The curious art and work something something something. (OK, I’m going to have to ask Lukas what this means)

It was translated by Robert Dossie in “The Handmaid to the Arts”, vol. 2, 1750, with various editions published later in the century. Now, it would be really good if I could get a copy of this, unfortunately there are not any I can find online for sale. Apparently they are very rare. But another of his books is available for only £150.
Nobody appears to have re-published it since the 18th century. I am finding this is a very common problem, whether I am after translations of Geber, or some 25th century alchemical works, it seems the last full reprinting was often done in the 17th or 18th centuries. Which is only to be expected, but it means that for someone like me who I only dabbling in it, information is very hard to come by.