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Glass Identification - Post here for all ID requests => Glass => Topic started by: ChrisStewart on September 08, 2007, 06:07:52 PM

Title: Slag Glass
Post by: ChrisStewart on September 08, 2007, 06:07:52 PM
Hi Cathy,

Davidson made slag glass in purple, blue and green.


Title: Slag Glass
Post by: Jay on September 09, 2007, 07:28:24 AM
Just to remind people that this particular 'colourway' is also often confused with designs by AD Copier for Leerdam. Though the models are clearly very different! (Copier's are definitely 'art Deco')

The Dutch term for the glass is 'Marmorite' and there is a well-collected group of boxes and tumblers etc which were made for the bonbonnerie chain 'Lindeboom' (1931-34)
The 'Lindeboom' set includes several simple round tumblers (cigarette holders. flowerpots) which can often be distinguished by the deco-style, rounded feet!
Title: Slag Glass
Post by: David E on September 09, 2007, 08:11:09 AM
Thanks for reminding us of that Jay - sometimes it's easy for us to just consider our homelands as possible sources! There is also a Bohemian maker from the 1930s although their output was mainly green, I believe.

As Matt mentions, I think the word 'slag' is rather derogatory - and misleading (if one believes the myth) so have tended towards malachite to describe it. However, the term 'marmorite' makes me think of Marmite (well known UK yeast-based beverage!)
Title: Slag Glass
Post by: Anne on September 09, 2007, 02:42:50 PM
I think the word 'slag' is rather derogatory

The slang usage of it is, David, but see for the proper usage of the word, which I believe comes from the German slagge - see etymology here:

Slag heaps were a very common sight at one time.
Title: Slag Glass
Post by: David E on September 09, 2007, 08:21:50 PM
Thanks Anne, but isn't this part of the urban myth

To quote Angela's Encyclopeadia:

"The name derives from the belief that these colours were achieved by adding "slag" from iron smelting works to the glass."

Just my personal preference, but slag glass tends to make me think it's cheap, low-end glass, whereas 'malachite' seems so much more sophisticated! :angel:
Title: Slag Glass
Post by: Anne on September 09, 2007, 08:50:33 PM
But see also Ivo's glass fact file for slag glass - "... effect achieved by adding blast furnace slag to the melt..."
Source:Ivo Haanstra, Miller's Glass Fact File a-z, p133
Title: Slag Glass
Post by: David E on September 10, 2007, 07:56:41 AM
I'm mailed Adam and hopefully he will drop by :)
Title: Slag Glass
Post by: Adam on September 10, 2007, 09:01:42 PM
Thanks for the nudge, David.  I was following this thread and might have been stimulated to reply anyway, but here goes.

1.  Nothing to do with glass, but Anne's comment made me cringe as have many others in the past, on TV, in the press etc.  "Slag heap" is the problem.  These heaps (I lived almost within sight and certainly within smell of several) were colliery waste, stone and low grade coal and had nothing whatever to do with slag.  In Durham they were always called pit heaps - I don't know what other areas called them.  I can't believe that anyone who knew what they were would call them "slag heaps", but I'm probably fighting a losing battle.  Thank you, Anne, for the chance to get that off my chest!

2.  "Slag glass".  I THINK that I only heard this horrible name in recent times (like cranberry) but I've been so brain-washed by newly invented words that I could well be wrong.  I presume that it means the same as "malachite" and I'm pretty sure that I learned that one in my youth.  As we didn't make the stuff in my time it would only be when looking at bits dug out of old furnace bottoms that old-timers would have used the word.

3.  Although I have no first-hand knowledge of the composition of malachite/slag glass I would be astonished if it contained any slag.  Why would it?  The old glassmakers (those even older than me!) used readily available waste such as horse manure, coal dust and coke dust (all produced or used on the premises) but the nearest blast furnace would have been many miles away.  I don't know the composition of blast furnace slag but I would guess that the only glass colouring agent present in significant amounts would be iron, and lots of it.  Looking (from memory) at malachite/slag glass I can't see a requirement for any iron at all.

4.  Never having had a bit of blast furnace slag in my hands I don't know what it looks like, but it might well have a swirly, marbled sort of appearance. If so, could "slag glass" refer to appearance?  However, please don't anyone start a new old wives' tale running from nothing more than that casual guess!!

Adam D. 
Title: Slag Glass
Post by: David E on September 10, 2007, 10:18:17 PM
Thanks for your input Adam.

My own feeling is that it was supposed to refer to its appearance, however, as malachite and marbled are already entrenched in the glass dialogue, I do wonder why it was ever referred to as 'slag' (a rather derogatory term IMHO) and when it was introduced.

Then again, as Anne points out, Ivo's Fact File does refer to the inclusion of slag from a blast furnace.
Title: Slag Glass
Post by: Anne on September 10, 2007, 11:22:50 PM
Adam, I'm glad I was of service.  ;D  Seriously, in Lancashire where I was raised, they were always called slag heaps, and Barry tells me that where was raised in West Yorkshire the same was true. In both cases we would be meaning pit waste rather than waste from other minerals.
Title: Slag Glass
Post by: ChrisStewart on September 11, 2007, 07:27:05 AM
Hi All,

Davidson called slag glass "marble glass" both in the 1880s and also in 1964 when they re-introduced it briefly.

I also remember seeing an article in the Pottery Gazette about making glass from iron slag. It was sometime in the 1890s. I'll see if I have a copy.