If you can, turn over the mold while injecting the wax so the
letters will fill. If this doesn’t work, powder the mold surfaces
with corn starch or talcum powder to make a way to the air to get
out. Also you might try to pump a bit harder to force the air out.
If you are using a mold clamp ( your should) try not clamping the
mold so tightly. If all of this doesn’t help, you may have to cut
air vents from the letters to the outside edge of the mold to allow
the air to escape.
The powdering will help the wax to release. We use a shaving mug
soap brush to apply the powder but you can use any good small
bristled large brush or you can use a puff (relatively fine
mesh/weave bag with powder inside and just "puff/pat the mold
surfaces to dust). Some folks use a powder puff (body powder
applicator puff). Lightly blow off excess with breath or compressed
If you can get the air bubble problems fixed without the use of the
powder, a good spray on mold release (Smooth-on Universal Mold
Release for one, but there are MANY out there) can be used for wax
release. If you are using vulcanized molds, there seems to always
be a problem with the wax sticking in the tapered injection nozzle
hole. But I have found that if you use a type of washer called a
"fender washer" (a washer that is large compared to the size of the
hole, ie. a 1.25" washer with a .25" hole) available at a good
hardware or auto parts store, putting this washer on the mold where
the washer hole lines up with the mold filling hole and then putting
the injector nozzle in the washer hole and filling the mold with
wax, the wax doesn’t stick so badly in the filler hole. This works
best if you are using a spray release (often/usually a silicon
material) but be sure to always release the 2 sides of the washer or
the wax really will stick to it.
Also, some waxes work better than others for different applications.
I prefer Serria Red ( and just because somebodies wax is red doesn’t
mean it is the same as Serria Red. Many like more flexible waxes
that the SR but I like it for cleanup and if any rework is needed (a
well cut/made mold will keep this to a minimum, but the key words
here are “well cut/made mold”).
If you still have problems, re post or write me directly and we can
talk more as to what your problems may be and what to do about