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Fiberboard molds

Posted: Sat Sep 20, 2014 6:52 pm
by Joe Wokovich
I have a customer that wants a long, shallow, and rectangular plant vase.
It needs to be about 42 inches long and no wider than 8 inches in width for the base. I have plenty of kiln room for this and I will be using 3/16 ths float glass.

My stumbling block is in making a support for this vase with no seam marks from support shelves.I have scrounged around and found some 2 inch thick fiberboard from some long forgotten source.
It is plenty long (like 60 inches) and almost 2 feet wide. I can cut this down for a nice seamless support and kiln wash it, but I am wondering if 2 inches is too thick to use. I guess I am wondering about how much heat will be absorbed by the fiberboard. I will be slumping over the fiberboard and think I should be able to pull a six or seven inch drape for the sides.

Anyone have any thoughts on this??

Thanks
Joe

Re: Fiberboard molds

Posted: Sat Sep 20, 2014 8:55 pm
by Marian
Fiberboard makes a fine drape mold. Are you concerned about adjusting the ramp up? Your regular schedule for slumping float should work the same. The board insulates but it will be on the bottom.

Re: Fiberboard molds

Posted: Sun Sep 21, 2014 12:32 am
by Kevin Midgley
glass too thin

Re: Fiberboard molds

Posted: Sun Sep 21, 2014 2:22 am
by Joe Wokovich
Kevin Midgley wrote:glass too thin
Thanks Kevin, I gave the wrong thickness, I'm thinking about 1/4 inch. Still too thin?

Re: Fiberboard molds

Posted: Sun Sep 21, 2014 2:26 am
by Joe Wokovich
Marian wrote:Fiberboard makes a fine drape mold. Are you concerned about adjusting the ramp up? Your regular schedule for slumping float should work the same. The board insulates but it will be on the bottom.
Thanks Marian, I've never fired over a mold this thick and was wondering before I did it. The only other thing I plan on is to put fiber paper around the edges of the fiberboard to make sure I can get the fiberboard out of the finished piece.

Joe

Re: Fiberboard molds

Posted: Sun Sep 21, 2014 11:57 am
by rosanna gusler
1/4" should be fine since you are draping over. Cut a piece of cloth (like a sheet or towel) the size of the glass you will use and let that drape over your mold to get an idea of what the finished product will look like. R.

Re: Fiberboard molds

Posted: Sun Sep 21, 2014 1:52 pm
by Bert Weiss
You should be able to purchase 1: x 24" x 48" fiber board. You can cut strips to put under the main board to define the edges.

I am a big fan of 10mm float glass vs 6mm. I can generally work it at lower temperatures which yields cleaner results. The strength and mass are better. BTW, when you bend the edges like that, it strengthens the glass. Be sure to put the tin side down. Otherwise you will get a rough inside surface.

Re: Fiberboard molds

Posted: Sun Sep 21, 2014 4:19 pm
by Jerrwel
Joe Wokovich wrote:The only other thing I plan on is to put fiber paper around the edges of the fiberboard to make sure I can get the fiberboard out of the finished piece. Joe
The fiber paper may not be sufficiently thick to allow the mold to release from the glass; my experience is with tested glass rather than float glass at 1225F which probably allows the glass to fall more however. I drape using fiber paper over ceramaguard fully expecting to break up the mold to remove it from the finished project. What will be the effect of the greater mass created in the corners of square projects? Rounding the corners may help if this becomes an issue. Sounds like a practice piece or two are in order. Look forward to reading what is successful with your project.

Re: Fiberboard molds

Posted: Sun Sep 21, 2014 4:23 pm
by Jerrwel
rosanna gusler wrote:1/4" should be fine since you are draping over. Cut a piece of cloth (like a sheet or towel) the size of the glass you will use and let that drape over your mold to get an idea of what the finished product will look like. R.
What a great tip. I'm sure I'm not the only person here who thanks you for this one!

Re: Fiberboard molds

Posted: Tue Sep 23, 2014 9:59 am
by Bert Weiss
With any mold material, the glass, the mold material, and the mold shape must be conformed to be compatible. When you are done, you want the glass to be intact and removable from the mold. Every material has a COE, that is relative to that of the glass. For the most part, if you encounter a problem, you can change at least one of those factors to get a successful mold.