Fiber board turns brown

[Linda Denli]

I am making a shape out of three layers of fibe board over which I will slump a blank made up of two thicknesses of spectrum 96 already fused together.

I had already made two layers and decided to add a third layer to give more depth. I cut out the shape from one eighth board, laid it on top of a square piece of the same board which was to be the bottom layer to hold the other layers (I planned to spray with fiber mold hardner so the shape would be good for a few fusings).

I putthe two pieces, one on top of the other, in closed kiln at a temperature of 1000 to burn off fibers. I opened the kiln at about 900 to vent and the board had turned dirty brown. It remained that colour when cooled and I have a horrible brown patch on my kiln shelf too!

Did this happen because I heated the kiln without venting and can I still use the mold?

Any help would be much appreciated - I seem to be having one of those days!

Best wishes

Linda

[Brock]

I am making a shape out of three layers of fibe board over which I will slump a blank made up of two thicknesses of spectrum 96 already fused together.

I had already made two layers and decided to add a third layer to give more depth. I cut out the shape from one eighth board, laid it on top of a square piece of the same board which was to be the bottom layer to hold the other layers (I planned to spray with fiber mold hardner so the shape would be good for a few fusings).

I putthe two pieces, one on top of the other, in closed kiln at a temperature of 1000 to burn off fibers. I opened the kiln at about 900 to vent and the board had turned dirty brown. It remained that colour when cooled and I have a horrible brown patch on my kiln shelf too!

Did this happen because I heated the kiln without venting and can I still use the mold?

Any help would be much appreciated - I seem to be having one of those days!

Best wishes

Linda

It sounds like all the binder has not yet burned out of the board. Go a little hotter, until it turns white again. You can still use the mold once all the binder has burned out. Your shelf will be fine. Brock

[Phil Hoppes]

Take the board up to at least 1400 for an hour or so and bring it down. That should burn off most of the binders. If the bottom is still brown/black flip it over and repeat the same schedule.

Phil