Products used in this How To:
One Piece Mold
one piece mold works perfectly for parts like this bulldog that
have a flat back side. The flat back side gives you a noncosmetic
side to pour from. The advantages of a one piece mold are the
simplicity of making the mold and no seam lines in your finished
casting. This particular bulldog was used for as part of a beer
tap found in bars across the country. This How To process will
walk you through the steps for making this one piece mold.
first thing you need to do is to fasten the part onto the mold
base. The base can be any nonporous material. Here we used a piece
of plastic. You can also use wood, metal, styrene, coated poster
board, or any other material you have available. No mold release
is necessary on your original unless it to is made of silicone.
Silicone rubber only adheres to another silicone. When you fasten
the piece down, try not to leave a gap between the base and the
part. The silicone will seep under the original and it will require
additional clean up later. It's much easier if you eliminate the
gap before pouring the silicone.
next step is to mix and pour the silicone moldmaking rubber into
the moldbox. Here we are using Dow Corning's HS II for the moldmaking
rubber. The mix ratio is 10:1 by weight. After properly weighing
and thoroughly mixing the rubber, we slowly pour from one corner
of the mold box. This slowly submerges the part in the rising silicone.
If you have a significant amount of detail you may wish to paint
on the first layer of silicone before pouring the rest into the
mold box. Painting the first layer of silicone prevents air bubbles
from sticking to the part and ending up with bubbles in your mold.
the silicone to fully cure. The demold time is 24 hours with Dow
Corning's HS II. Once the silicone has cured remove the glue or
clay that sealed the box to the base and begin to remove the mold
from the box. Here we are using a putty knife to slide underneath
the mold and the bulldog to break the glue off and remove it from
is to trim the silicone in the pvc pipe to allow us to remove the
silicone from the pvc.
trick of the trade is to using rubbing alcohol to help remove the
silicone from the pvc pipe. The rubbing alcohol will make the silicone
very slippery which aids in it's release.
then slide a dull knife around the outside of the mold which allows
the rubbing alcohol to seep in and make the two very slippery allowing
us to simply pull the mold out of the pvc.
that is left is to remove your original by flexing the silicone
mold and removing your original.
you can see the original next to the mold that picked up every
single bit of detail. Your are now ready to mix up your Alumilite
resin and cast your perfect replica of your original.