Why to cool or mabe I should say "hot"

http://www.thisiscolossal.com/2014/10/artist-carol-milne-knits-with-glass/

 

Comments

Thu, 10/16/2014 - 23:16

SallyE (not verified)

Wow, that is a tour de force of glass casting!  The easy part is making the wax mold, since wax at the correct temperature is easy to work.   Then you have to encase it in a refractory mold and steam / boil out the wax and totally dry out the mold.  

Now for the hard part - you have to get the glass particles into all those little turns and twists.   Glass powder / frit reduces in volume as it melts because the air between the particles is driven out.  So, you also need to have a source of glass to "feed" the mold as it fires because no mold can hold the amount needed on it's own.   (Usually firing is done upside down so you feed from the bottom.)  

And glass won't flow into places that are too small - think thick honey trying to flow through a thin tube.  The hotter the glass, the less viscus it it.  But, the air bubbles are also trying to raise through the glass.   This must be a VERY long firing schedule - Days or maybe weeks.

After cooling (another long time), you have to carefully break off the mold in tiny pieces - think dental tools.   And then there is the tedious work of trimming off the excess glass if any and making it sit flat.   The issue here is accidentally breaking it.

A real tour de force.   I'd love to see the firing schedule she used.

Fri, 10/17/2014 - 04:01

SallyE (not verified)

Michael,

Thanks for the links!   I took a hot glass casting class a few years back.   The difference in what you can make, is that with hot casting you can't do much in the way of undercuts because you press your master mold into a mixture of slightly moist sand and bentonite.  You then have to pull your master out of the sand to be able to pour the glass in.   The glass is at 2200 - 2400 degrees - glass blowing temps.   It is a process that is almost as fast as blowing glass

When you use a plaster cast and fill it cold you can do just about any shape.   But it's a LOT slower process and typically you process the glass at between 1500 and 1700 degrees.

That is why glass people refer to themselves as working cold (stained glass), warm (fusing and plaster casting) or hot (blowing and sand casting).   I do cold and warm but not hot.   Hot requires a different kind of kiln than I have, and I don't like working hot anyway.