Making latex molds

Always good idea to use a release agent. I use a very thin coat of Vasaline.

BTW...making a mold...You can speed dry buy using a hair dryer between coats. Also add gauze after 5-6 coats and the mold will be stronger and last longer.

Taylorra

     The pictures show the results of molds made from foam products of the wall and portals. The portals can be broken and made to a custom width if you cut some pieces to make the extensions. India ink in alcohol gives the initial coloring. Weathering will follow. They are made from plaster as it dries in 30 minutes. The only release agent was wet water in the molds.

     Unfortunately I have no pictures of the actual molds. There are a few details that worked for me after trial and error. I used plexiglass as the base holding the wall as latex will stick but peel off when dry. The coats must be very light and dry over night. The first will kind of hold the mold in place. After about 5  coats I used wide drywall mesh laid over and then another 6 or so coats. Again thin so it seeps into the details.

     When satisfied, I created a fence around the mold with some old wood trim. On top of the mold I put silicon cork and smoothed the whole back more or less level. This will allow the mold to stay flat when it is used but still be flexible. It will take two weeks or so to make but the molds will be worth it. I use plaster since it cures very quickly. Good Luck.

Ray Marion

Ray

Your brick molds make a very realistic looking retaining wall.

Good job.

Ray; Your work looks terrific.  What do you use to clean your brushes between coats?

  Did you use a release agent?  Can you make more than one mold and combine them?  I think I have the same master you used. Mine is from Ultimate Scenery in Ohio.  The master is 5 inches by 12 inches long.  I need to cast sections 10 inches tall and would like to make a mold 24 or 36 inches long.  I have about 25 feet to cover.  Any ideas on how to do that?

Clean the brush with warm water between each coat and dampen again before each coat. Use a cheap brush (1" width) because after several coats it will be loaded with latex particles.  I use wax paper as a base under what is being molded.  Don't forget to put the gauze over a wet coat of latex, hit it with wet water, tamp it into the form with the brush and cover it with another coat right away.  Err on the side of adding more rather than fewer coats.  After the final coat let the mold sit for a few days to cure before releasing. And it will improve the strength of the mold if the final curing occurs in a warm room.

Overall, not complicated, just takes time and patience.

Poppyl

Clean the brush with warm water and handsoap, minimal suds. This will help remove alot of the latex. You should use a bush that will need to be discarded when done. I did not use a release agent in creating a mold but used a little soapy water when casting. The latex doesn't seem to stick to the foam. You will noy put too many coats on and make sure they are thin and dry totally.

     The size of the mold you want to make might be a little large if you cast with plaster. You only have about 20 minutes to work before it hardens and that size would be a lot of plaster to mix. If you use other materials they need hours to days to cure. That may preclude using a bigger mold.

   Using a coping saw you can cut a hard cast to the size you want. If you use the pilasters like in the pictures, the longer length is not needed. The pictures are about 90' of wall and it was done in two days by myself. There was tons of input from club members and micrograms of help. Typical, but lots of fun and satisfaction.  

     I will take a picture of a finished mold tomorrow and post for you to see.

Ray Marion

Here are two pictures of the same mold for a portal. You can see the mesh embedded and silicone on back for support.

Ray Marion

BTW, I forgot to mention that wet water also works well as a release agent.  Spray the item to be molded right before applying the first coat of latex.

I also spray the inside of molds with wet water before casting to get a good separation once the casting has cured.

Poppyl

Hello guys, I am SFX makeup artist and do lots of props professionally.

  One: soak you brush in ammonia and water, ammonia is the preservative for Latex, it will keep the latex from gumming up on your brush and help it flow.

While woodland scenics is good latex, craft store latex mold material is cheaper and has a better body.

use PAM as a release agent, you can later wash your master with Dawn and remove the oil easily.

the same PAM can be used in the mold when casting.

 I use spandex in the mold in the last layer, and do wet the spandex or fabric with ammonia and water to help the latex absorb into the fabric.

the mountain man

    Thanks for the tips. I forgot about the ammonia. The Pam is an excellent idea. Could you give more details about where you obtained spandex?

Thanks

Ray Marion

I bought liquid latex from a craft store.  I used wet water as a release agent.  I use a piece of glass shelf as my base.  I sprayed the object I wanted to create a mold from and brushed on a coat of liquid latex.  I let it dry over night and return the next day and put on another coat.  I just store my cheap one inch paint brush inside a zip lock bag and reuse it.  If the latex starts to gum up I just peal it off the brush and keep going.  You can use a hair dryer or heat gun to speed up the drying process, but I wasn't in a big hurry.  After five or six coats I cut a piece of mosquito netting and stick it on the wet latex mold and add some more liquid latex to cover the cloth.  The mosquito netting I found at a fabric store.  1/3 of a yard gave me plenty.  So far I have made three molds.  Two were copies of rock walls and one is a large piece of coal that I liked the strata.  I just covered the side I liked and let the latex extend down the sides to form the edges.