Wet felt and moldable fiber blanket are both names for ceramic fiber materials that have been treated with the rigidizing solution collodial silica.
When wet felt is allowed to dry, it becomes rigid and capable of holding the shade of an original model. The wet blanket will only shrink about 2%, which makes it a good material to use when exacting forms are desired.
Some fiber mold hardeners also contain ethylene glycol keep them from freezing. However, wet felt must never be frozen. Therefore, it is usually not shipped during winter in cold climates. During that period of time, wet felt can be prepared from dry fiber blanket and liquid mold hardener.
MOIST PACK INSTRUCTIONS:
1) Center the wet blanket over the model and massage it firmly to the contours of the model. Allow a lip of excess blanket at least 1" larger than the model. Any extra blanket can be trimmed and stored in a sealed plastic bag.
2) Allow the blanket to dry thoroughly before attempting to remove it from the model. It is best to dry the blanket for 2 - 3 days, although a heater facing the mold of a hand-held hair dryer will speed up the process. DO NOT USE YOUR OVEN - the fumes will contaminate your food.
If the blanket is to be kiln dried, DO NOT EXCEED 175°F (79°C). The kiln should be VENTED & FIRED SLOWLY.
3) If you wish to sand the surface of the mold, wear a respirator and have a vacuum in one hand to keep the dust out of the air. It is better to fill any surface imperfections with kiln wash, or a special blanket filler (such as Luminar Mold Mix) which is designed for just this purpose.
4) Prefire the fiber mold to 677 - 704°C (1250 - 1300°F) before using it.
MAKING A MOIST PACK MOLD USING A DRY FIBER BLANKET & MOLD HARDENER:
1) Prepare a model or form to be duplicated and place it on a board covered with plastic. Seal the edged of the model to the board with plasticine and coat all surfaces with a release agent, such as cooking oil spray.
2) Cut a piece of 1/2" thick fiber blanket slightly larger than the model. If you can only find 1" thick blanket, gently peel the blanket into two 1/2" thick sheets. (The 1" blanket is too thick for the hardener to penetrate, and it will leave a soft center.)
3) Place the blanket on a shallow tray or sheet.
4) Wearing protective gloves on your hands, pour the mold hardener over the blanket. Apply light pressure to the blanket to make sure it is saturated with the solution. Use approximately one pint of the liquid for one square foot of the blanket. The excess solution can be poured back into the container.
5) Follow instructions 1 through 4 under MOIST PACK INSTRUCTIONS above.