Author Topic: Apsley Pellatt, the Falcon Glass Works, London  (Read 2497 times)

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Offline David E

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Re: Apsley Pellatt, the Falcon Glass Works, London
« Reply #30 on: February 07, 2010, 10:25:02 PM »
With regard to frit and the terminology (mentioned earlier in this topic), I had a reply from Ray Drury:

Quote
Yes I mean that 80% was cullet and 20% frit. [I queried the ratio - DE] There was not a lot of frit in evidence in the chutes down to the batch feeder which continuously fed the Rolled Plate furnaces but when it came to other glasses, possibly pot melted the proportion of frit could be almost anything. When we were making coloured rolled plate much more frit was used to get the colour.

So it would seem that both Chance and Pilkington used the term 'frit' to mean the sand mix.
David
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Offline David W

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Re: Apsley Pellatt, the Falcon Glass Works, London
« Reply #31 on: February 19, 2010, 06:39:23 PM »
Adam,
Many thanks for your explanation. I am sure it is not the first time that practice has not behaved according to theory. I was moved to look up another glassmaker , Harry J. Powell,  Glassmaking in England. He, page 13, quotes another ancient , Theophilus (c. 1140), as follows:-
“A mixture of the extracted alkali with sand and a small proportion of lime was heated in the calcar (a type of reverberatory furnace) until partly fused. When cool the fused mass, called “frit”, was broken into fragments and shovelled into crucibles standing in the melting furnace. In the crucibles the frit melted, became fluid and threw to the surface a scum of impurities. After the scum had been removed by skimming the remaining glass was ladled into pans of water. The water was drained off and the glass, when dry, was replaced in the crucible for final melting.”

Unfortunately,  according to this translation, Theophilus does not explain the workings of the fritting process although it becomes clear that the batch ingredients leave much to be desired.  I don’t suppose that you were troubled with scum, ladling into water etc.

It is always dangerous to try looking up the original text and when I turn to the translation of Theophilus by Hawthorne & Smith (Dover Books, 1979) I read :-
Chapter 4. The Mixture of Ashes and Sand.
“When you have arranged all this (i.e. built the furnace), take beechwood logs completely dried out in smoke, and light large fires in both sides of the bigger furnace. Then take two parts of the ashes of which we have spoken before, and a third part of sand collected out of water, and carefully cleaned of earth and stones. Mix them in a clean place, and when they have been long and well mixed together lift them up with the long handled iron ladle and put them on the upper hearth in the smaller section of the furnace so that they may be fritted. When they begin to get hot, stir at once with the same ladle to prevent them from melting from the heat of the fire and agglomerating. Continue doing this for a night and a day.”

That’s it. There is no account of what to do next as the Powell version suggests. And there is no mention of frothing.
How one equates these two quite different accounts is a problem. It has been suggested that Theophilus got his account from an even earlier one by Binguccio. Perhaps Powell was quoting the wrong author!
What is annoying though, is that although Powell explains all this historical stuff he does not say what they actually did at the Whitefriars works.

There is no need to reply that you did none of the above.


Offline David W

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Re: Apsley Pellatt, the Falcon Glass Works, London
« Reply #32 on: February 26, 2010, 05:55:31 PM »
Adam, Re the term "frit"

I have just by chance come across a published Royal Institution lecture of December 8, 1933 by a Major R.M. Weeks, a director of Pilkington Bros.
In this lecture entitled "The Making of a Sheet of Glass" he first describes the batch components in some detail; he then says " Having mixed the raw materials, or frit as it is called, the next step is to melt it...."
So this fully supports the accuracy of your definition. Incidentally, there is no mention of any frothing, either when filling a pot by hand or mechanically for a tank furnace.

I also tried the GMB search facility for the word "frit" and was rewarded with a long list, some with a somewhat muddled understanding of the meaning of the word, such as picking up fragments of broken glass on the marver with a hot paraison. So it does seem that this is a word that needs to be defined for the context in which it is used.

One contribution that I had not previously noticed is that Pellatt records that he fritted (baked) his batch before use. Another suggested that the composition of fritted batch was not changed by the subsequent melting. I think this might on occasions be true but on most occasions some further change must have occurred as part of the founding process if the fritting, which should fall short of actual melting, was properly carried out.


 

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