Digging at the Whitall Tatum factory?

[baltbottles]

My opinion is that warming of metallic molds probably started quite early. If you blow molten glass into a cold mold the glass cools too quickly and the bottle fractures causing the blow to fail. This does not occur if the mold is heated before blowing. Allowing the glass to still be warm enough to finish the lip and transport to an annealing oven. Once glass cools to below 1015 degrees without annealing it quickly cracks.

As for the mold warmers I would bet these were made through out the day to keep the mold at a working temperature. I am surprised that any of them survive without annealing. And I would also bet that most of them got used as cullet in the next batch.

Chris

 

[AntiqueMeds]

most of them got used as cullet in the next batch.

no doubt. The existing ones were likely dug from the glass house cullet pile.

A solid chunk of glass like that is probably going to survive a less than optimal cooling curve better than a bottle with relatively thin glass.

 

[Plumbata]

I'm sure that many were recycled, but just the same, I'd imagine that many were tossed on the floor and swept up and tossed in their dump. The energy needed to collect and sort several pounds of differently-hued glass, especially when mixed with the filth and contaminants on the floor which would be bad for the batch, was probably better expended doing other more productive things. Also, I could see the glass being recycled more regularly in 1850 versus the early 1900's; the era apparently represented by the very interesting pieces pictured.

I bet a bunch of those things are waiting to be dredged up from the river adjacent to the property. If I lived in the area I'd be there searching right now. []

 

[AntiqueMeds]

cullet had to come from somewhere. Probably better to first sort it on the site than to pay contractors for it?

 

[tigue710]

ORIGINAL: baltbottles

My opinion is that warming of metallic molds probably started quite early. If you blow molten glass into a cold mold the glass cools too quickly and the bottle fractures causing the blow to fail. This does not occur if the mold is heated before blowing. Allowing the glass to still be warm enough to finish the lip and transport to an annealing oven. Once glass cools to below 1015 degrees without annealing it quickly cracks.

As for the mold warmers I would bet these were made through out the day to keep the mold at a working temperature. I am surprised that any of them survive without annealing. And I would also bet that most of them got used as cullet in the next batch.

Chris

Ive wondered myself how or if they warmed the molds prior to the practice of using mold warmers like this... Ive dug quite a bit at the willington and new london glass house sites, but have never seen any fragments of mold warmers at either, lots of drips, frags, cullet, chunks etc., I wonder if they used some other method? I think as long as the mold isnt ice cold the gather warms the mold sufficiently but not without some deformities like whittle. This brings me back to the wing thingamajingy, or mold pinch, that obviously cooled quickly enough to solidify just being pinched by the mold...

 

[AntiqueMeds]

The mold temperature is always going to be way below the fluid temperature of the glass. That mass of iron is going to suck a lot of heat out of the glass as soon as it touches it bringing it down to the semi plastic temperature. You really want that though or you could never use the snap case on the glass after you pull it from the mold.

 

[baltbottles]

Matt,

I would bet they just heated the molds up in a small chamber of the furnace that didn't get super hot possibly an annealing over or perhaps they just had a special oven for warming molds. It is also my belief that most molds made before the 1850s were probably made of brass rather then cast iron. And likely had much thinner walls so they cooled quicker so they probably had to keep them in some kind of warmer between each bottle being made. Also Brass melts at a lower temperature then molten glass so I would bet the early molds would not have been able to stand a solid pour of glass in them without damaging the mold. Later heavier cast iron molds would have been able to take this kind of abuse.

As for the pinched fin of glass I have been talking to a glassblower that has a studio a few miles from my house and he agrees with me about them being a pinched fold from closing the mold. He said that if I can get my hands on a mold we could do an experiment. I haven't had any luck getting a mold so I have been thinking about going to a local machine shop and seeing what a simple round mold might cost to have made. If I can get a cheap mold then I can finally test my theory and put that stupid mold pinch to rest.

Chris

 

[Plumbata]

So do you think the molds were specifically Brass, or any copper-based alloy resembling Brass or Bronze? Stuff like arsenic, antimony, etc might have been alloyed to make a more wear-resistant mold. Copper alloys tend to transfer heat more easily than cast iron, and being generally heavier and more inexpensive it would make sense that they were thinner-walled and kept heated in a special chamber.

Would the molds have been made at the glasshouse, or would they have contracted with bell-makers to prepare and cast the molds?

I just found a table and apparently the copper-rich Red Brass has the highest melting point of the variety of brasses (990-1025 Celsius), and is well above Bronze, so would that likely have been used? Isn't there part of a copper-alloy historical flask mold in some glass museum out east? Someone posted a picture a year ago or so ago.

On the subject of molds, is there any evidence of carved soapstone/steatite molds having been used in early American glasshouses? Perhaps a simple carved dip-mold?

 

[kungfufighter]

ORIGINAL: PlumbataIsn't there part of a copper-alloy historical flask mold in some glass museum out east? Someone posted a picture a year ago or so ago.

Lafayette GI-85 (the "A" variant if I recall) at Corning...

 

[Plumbata]

Spot-on as usual Jeff!

Here's a pic;

The site claims that it is a Brass mold, but without being able to mess with the piece it looks like Bronze or yellow brass. I'd love to dig up something like this! []