Mold bits in my casting

[Cristi L]

Hello all- I've been playing with lost wax....loading the empty mold with frit, then firing.
Everything is working well, except for one darn thing. Bits of mold schmutz caught in the glass.
I could just use a flower pot to hold the glass overhead, but that would require me working smaller (God forbid)
Or a taller kiln, which both my pocketbook and available space forbid.
I see the mold loading technique in reference materials everywhere, so I assume (dangerously) there is a piece of information I'm missing. Any suggestions? Many thanks- Cristi

[Morganica]

Yep, it's an ongoing problem when you work with plaster/silica refractory molds. There are lots of ways to limit the risk of this happening. Many are just common sense:

--Use the correct water:dry mix ratio, preferably kept on the low side (a dryer mix is usually stronger)
--Make sure you've properly cured the mold before you put it in the kiln (giving it 24-48 hours to cure makes for a stronger mold)
--Don't mess with the mold surface more than you have to, to avoid cracking/chipping details that could later come off during firing
--Trim the sharp edges and points off the mold and smooth them out; this helps prevent accidentally knocking into them and chipping them off (or expanding/contracting cycles doing this) so that they fall into the mold cavity
--Whenever you trim the mold, put a piece of paper/cover over the opening to keep stuff from falling down inside
--GENTLY vacuum the crumbs of plaster out of the mold--I use a damp paint brush to pick up the rest of the crud
--Keep your upramp schedule slow and steady, and make sure your mold is fully dry before you start up
--Don't pack frit hard into the mold, especially if you're packing into a lot of heavy/angular details
--If you are steaming wax out of the mold: DO NOT OVERSTEAM. And when you're through the steaming step, let the mold dry thoroughly, then clean again. You'll probably find more broken bits released by the wax as it traveled down the mold.
--As you suggest, drip in glass from the outside. You don't have to set up a full reservoir; you can set up a perforated stainless grid on kiln furniture, suspended over the mold (or sometimes I just set the grid directly over the mold opening). As long as you can get enough glass on the grid, it's softer on the mold

The biggest deal, I've found, is to make sure that the mold is absolutely clean and free of any dust, loose particles or potential cracks/loose particles before you start. That stuff just seems to make its way into the mold too easily.

[S.TImmerman]

Cynthia, when are you going to take all your words of wisdom and have it typed up into a book? I'll bet most of its out there and you just need to organize it?

Sign me up please ..

[Morganica]

LOL...maybe when MY glass comes out of the mold completely schmutz-free, Sharon.

[Cristi L]

Thank you so much.....
I can now see schumtz free castings on the distant horizon.