Post #578520 by MauiTiki on Wed, Mar 2, 2011 5:09 PM

Here is my "How to make a mold" contribution to TC... Lots of Photos, not so much words...

This mold was made from a slip cast mug that I modified and customized.

I wrap clay around the bottom and fill it with plaster to make the bottom part of the mold.

Carve some alignment holes in the plaster bottom. Next I fit it in to my custom ADJUSTABLE box and add a cone of clay at the top for pouring slip in and out. It should be a couple inches tall as the slip level drops about an inch during the casting process.

Another angle...Don't for get "divots" to help the mold line up correctly.

Pour plaster so that it's about 1.5 inches thick on the top of the mug. This plaster isn't very smooth because I spent too much time mixing, it should have been poured sooner and probably could have used more water. FOLLOW THE PLASTER MIXING INSTRUCTIONS!

I flip the box and remove the clay.

Paint on some "soft soap" so the plaster won't stick to itself and pour another layer of plaster. I mixed this plaster much better this time after learning from the other side.

When it's dry you can remove it from your box.

Take the clay out of the top and you should be able to pull apart the mold. Because I used a slip cast Mug as my master it soaks up the water from the wet plaster and becomes soft. It tears as the mold comes apart. Most of it easily peels out, but I have to hose "Power wash" out the rest of the remaining original.

Let the mold sit in the hot sun for a day before using it for the first time. I leave a fan on it too, to help the drying process.

Whoo Hooo!! now you have a mold. I pour slip, let it sit for 35-40 minutes before pouring out, then I let it sit for a minimum of 1 hour before removing it from the mold. Often I leave it overnight and remove the mug in the morning. Watch the slip level too, sometimes you need to add more slip if it starts to drop too low in the mold.

Good Luck!