Question:

How do I make molds?

Dis-assembly

Before casting a multiple-piece mold, take it apart and examine it so you will know which piece should be removed first after the slip has been poured and the greenware is ready to be removed. To help you remember the disassembling order in a multiple-piece mold, use a waterproof marker to number the pieces. If there is something special that you must know about a particular before casting it, such as “drain with straw”, mark the outside of the mold with a waterproof marker. Once you have examined a new mold for any breakage and are ready to pour. Look it over one more time to see if it has any special problems you will have to cope with such as a small pour hole, undercuts, tricky draining etc.

Drying

It is important not to dry your molds too fast. Store them on slated shelves so that the natural air can circulate around them.
When buying a new mold be sure you always open it immediately to inspect the inside for any damage.
When cleaning the inside of a mold, never use anything other than a brush. If you encounter a stubborn piece of clay simply roll some waste clay into a ball and pounce it off.
Since molds work on the principle of absorption, it is important that you avoid touching the inside with your fingers. You do not want to leave any oil residue that may clog pores.
Be sure that you remove all dried clay from the seam area of a mold. It can dry and when you put the mold back together and start pouring again, the dried clay may warp the mold and eventually cause rust spots on your molds.
You may notice a fuzz on your molds when they are being sorted. This fuzz is caused by deflocculents in the slip that have penetrated the mold. You should remove this fuzz as it will harden and plug the pores of the mold.

Canvas Molds/more ideas

Put the canvas over a plywood box. Staple the canvas to the outside of the box. Again, the curvatures can be modified by how tightly you pull the canvas. You can staple just two ends, or all four ends for different effects. If you want to make this more versatile, make a version where you can vary the amount of curvature. Attach screws or nails to the outside of the box.
Or, (I'd rather think of a better idea than go to the trouble of making a plywood box), how about using clothes baskets! They come in round or rectangular, and are inexpensive.

Wood Molds

Wood
Wooden bowls can often be used directly without any coating. Wood is porous so clay doesn't stick. Keep an eye out for wooden bowls at garage sales.

Mushroom mold/description

It is useful to have hump molds elevated off the work surface so your clay can extend past the edge. This also makes it easier to trim the bottom if you want the clay even with the plaster surface. You can do this by adding a foot to the hump mold (making a mushroom mold).

Specialty Gypsum Products

Specialty Gypsum Products

Hydrocal FGR - A unique high strength cement with glass fiber used for fabricating glass- reinforced architectural details that are lightweight, fire resistant and thin cast.

Duracal Cement - Designed for concrete patching of highways, bridges, loading docks, etc. Can be drive on 60 minutes after set. Could also be used for outdoor statuary.

Hydroperm - Permeable metal casting product formulated with Hydrocal Gypsum Cement. Suitable for nonferrous castings because of smooth mold surface, carvability and controllable permeability.

Canvas Molds

Canvas
You can make a sling out of canvas and use that for your mold. For example, take a piece of canvas and put it over the top of a large round garbage can. Where the canvas overhangs the can, wrap tightly with string. Place your slab on the canvas. You can get different curvatures depending on how tightly you pull the canvas. This same technique can be used with buckets for smaller slabs.