Topic: Sucking on an iron when making glass - explanation needed please?

[flying free]

I am the first to admit that having only made a paperweight, and a funny shaped bowl and a funny shaped glass, I have no idea of the ins and outs of making glass.

So I am confused and looking for explanation for something please.

In the book Decorative Victorian Glass - Cyril Manley, pp 45, writes in relation to the making of silvered glass for Varnish & Co,  that a Tom Hill at Whitefriars glass showed him how to make double walled glass and says :
'Firstly, there were a number of ways to fold the glass back into itself, but only one correct way to get even folded specimens with a minimum number of failures.  This was to suck as soon as the blowing operation was completed.  The top of the article collapsed into itself, with the rounded edge absolutely free of ripples or corrugations. ... After the demonstrations, he suggested why the production of this type of glass was of such short duration.  The action of sucking hardened the blower's lungs, because the heat from the article entered the lungs.  He remarked that only a fool would make more than one!' (my underlining)

This sounds completely bizarre to me.  Why would Tom Hill damage his own lungs by doing this?
Is this correct?


Furthermore, I read this some time ago and thought it was completely weird and couldn't be true, but then in Charles Hajdamach's British Glass 1800-1914, I read this tonight:
pp269-271 Under the chapter Silvered Glass

Charles is discussing silvered glass (double walled 'mercury glass' as it is sometimes called) and talks about Malcolm Andrews attempting to blow a goblet based on Varnish glass.  His efforts were successful and Charles goes on to describe how they were achieved. There is a lengthy detailed description of each stage and then it says:
'Back on his chair, the glassmaker eases in the inner wall with wooden pucellas while the assistant helps by sucking gently at the other end of the iron[/u].'

Is this true?  is this possible?

Am I just horrified and confused in equal measure about something that is not what it sounds like?  I am sure I must have misunderstood this somehow.

m

[KevinH]

Hi m,

The info in Manly was something I was planning to add to the mercury glass thread, as a "probably implausible reason for the ending of mercury glass manufacture". But for now, that thread, as you know, is still in flux.

My own opinion of what Manley has said, is that Tom Hill probably did demonstrate a basic method of collapsing a double-wall vessel with the assistance of sucking air out of the cavity. However, I also suspect Mr Hill was taking a leaf or two out of Pellatt's thoughts on how "millefiori" glass was made by sucking out air from a "U" shaped double-walled vessel. (You will no doubt remember our discussions on that one.) What is not stated in Manley, is whether any of the options offered by Mr Hill included reheating of the upper parts of the vessel and using gravity as the initial and main source of collapsing power. Sorting out the smoothness of the collapse and ensuring non-adhesion to the outer wall would probably have been a trickier part of the process.

Like you, I have had minimal experience in manipulating glass. But I did form a reasonable base to a paperweight by standing the iron upright and allowing the reheated weight to drop downwards under gravity until a basal indent was produced. I was intrigued at how simply it happened and it made me aware of how too much reheating would cause a disaster during working!

I have no problem with the idea of an assistant helping the final "easing in" of a partially collapsed upper section of the vessel by gently and slowly withdrawing air.

But maybe our glassworking experts can add a comment or two?

[flying free]

quote 'I have no problem with the idea of an assistant helping the final "easing in" of a partially collapsed upper section of the vessel by gently and slowly withdrawing air'

But exactly how would they gently and slowly withdraw air?

Charles is specific on his description - it's just weird.

m

[Fuhrman Glass]

This is a true description of what was accomplished.
One also sucks the air from one's blowpipe when using a "pineapple" mold that has undercuts and thus collapsing the bubble to allow it to be removed from the mold. Normally one does not suck air from the pipe but in special instances it is done. It is not easy and requires a good amount of practice to achieve this. By the way, the air is normally not hot by the time it reaches the glassblower's mouth or enters his or her body. Timing and knowing when the glass is at the exact temperature to achieve these techniques and how hard and long  to suck was a special talent and remains that way even today.
 I have taught many students and as hard as they may have tried to make mistakes and suck some hot air, they were never able to achieve getting any hot air to their mouth. The greatest problem was that the blowpipe would get extremely hot and would then have to be quenched with a pipe cooler or wet papers that would reduce the temperature of the pipe itself.

[flying free]

Thank you Tom!

So, perhaps Cyril was 'mislead' by the 'hardening of lungs' story.
It does perhaps mean then that these glasses were made like this, taking into account the Whitefriars experiment with Cyril there and also Malcolm's experiment recounted in British Glass.

ok, but ... just because a Whitefriars blower knew how to do it, this doesn't mean the technique was unique to Whitefriars and since many were made in a variety of Bohemian factories, in Germany and in Belgium, France and the USA (source Das Bohmische Glas Band III pp 130)  there must have been many places that knew about this technique.

m

[Fuhrman Glass]

 without a doubt many knew of this technique but mastering it was another story. as I recall there were some wine carafes that used a similar technique where there was a recessed reservoir where there was ice placed and then the wine was in the main container that allowed you to pour the wine and ice just cooled the wine and the wine was poured from a spout opposite the ice reservoir.
the more I think of this in making goblets, etc. the outer layer of glass may have had to be blown into lightly as the center section was formed with the wood jacks, otherwise the outer bubble might have collapsed as the inner portion was tooled inward. This probably required some selective heating of different portion of the bubble to allow parts of it to be formed as the outer bubble retained it's form.
I know this sounds cryptic and hard to understand without some visuals or drawings.

[flying free]

It does, but I think I know kind of what you mean.

I'm sure these were complicated to make.  Added to which , some of them were cased in coloured glass and then silvered, then cut.  Imagine being the glass cutter on the final stage of the process - you wouldn't want to make a mistake and damage that glass.

I have one that has a gold interior.  I've still not worked out exactly what method was used to do that process.

m

[KevinH]

I have one that has a gold interior.  I've still not worked out exactly what method was used to do that process.

Oh, come on, m, please ... we need a photo not just a description that is open to misunderstanding. 

[flying free]

oh mine is not English but is Bohemian.  It's on the board.  It's rarity is that it has a makers mark on the pontil plug.  According to my German book, that maker is a mark they did not have at the point the book was written

I'll link it.

m

[flying free]

http://www.glassmessages.com/index.php/topic,64357.msg360704.html#msg360704