WarmGlass.com

Hi

Could you please let me know the formula for calculating weight of glass for potmelts?

I will be using BE, Gaffer and Blackwood (not together).

Can calculate volume of a square and of a circle, but there was something of using this volume and the specific gravity of the glass...did this 10 years ago and can't remember how.

I think BE specific gravity is 2.5? Do I multiply the volume by the specific gravity?

Paul Tarlow has an excellent calculator on his website, but I often like pencil/paper/small calculator on my table.

Not having to open a digital gadget all the time gives me the illusion of being slightly smart

Many thanks and best regards, seachange

Seachange,
If you have calculated volume in the metric system, you multiply that by the specific gravity (2.5 as you said)
Stephen

Yes, 2.5 is specific gravity of Bullseye.

I believe you also have to add 10% to allow for the glass that sticks to the pot.

If you’re trying to calculate the volume of an irregular-shaped object (say a plaster mold for a sculpture), you weigh a large container of water, fill the mold with water to the level you want the glass (pour the water out of the mold,) then weigh the water container again. Subtract to find the weight of the water used, then multiply by specific gravity.

Many thanks to you both. By the way, Gaffer specific gravity is 3.6 if anyone is using it.

Best wishes, seachange

This made me curious about the specific gravity of recycled glass cullet, which I use sometimes.

Surprise - it is also 2.5 (well, 2.49 if you want to get picky).

http://www.penndot.gov/ProjectAndProgra ... 061513.pdf

FusedLightStudio wrote:If you’re trying to calculate the volume of an irregular-shaped object (say a plaster mold for a sculpture), you weigh a large container of water, fill the mold with water to the level you want the glass (pour the water out of the mold,) then weigh the water container again. Subtract to find the weight of the water used,

Is this any different than pouring water into the mold to the desired level, then weighing that water? I'm not trying to be contrary, just curious. Since you can tare most scales, this would seem easier/quicker/less math.

Best, Dana

Dana - I had the same question when taught this (last month at Arrowmont).

The reason is that the plaster mold, being dry, quickly sucks up water, so even in the time it takes to pour the water, make sure it's the right level, then pour it out to weigh it, the mold will have absorbed some of the water and it won't be accurate. Even moreso if you try zeroing the scale to the mold weight - you'll be including the weight of the water absorbed into the mold.

Might seem trivial, but, when I weighed the water twice in the same mold, the number was about 10% different.