Hi Dave welcome to the world of hot wax and air pressure. Ain’t
I’ve made RTV molds of about 60-80 waxes – all small – over
the past several months. I have had good success with this,
generally. The two point that I’d like to make to you is that, if
you are doing more than a handful, you may have to try several
different RTV rubbers before you get one that has the appropriate
rigidity for your application. One of the compounds which I
tried was from Rio Grande, their Ditto 3D. I found this very
soft and squishy upon curing. It is so soft that I don’t like
using it for injection waxes. This is because I have to squeeze
the mold halves togehter with some force to prevent the injection
wax from squirting out the sides or – worse – out the back end,
toward me. (I’ve tried dropping my air pressure and adjusting the
temp., but it seems that for my pieces and the wax I’m using I
must stick with the pressure and temp.) The second point is that
wax shrinkage may be an issue that you’ll have to deal with. When
your original wax was made it shrunk, perhaps 1 or 2 per cent.
Now, when you make a second-generation wax that, too, will
shrink 1 or 2 per cent. The cummulative effect of this is that
your final wax has shrunk 2 or 4 per cent from the original. This
may or may not be a concern for you, but only you can just this.
If, however, the waxes involved shrink more than this amount, you
can increase the shrinkage problem by whatever cummulative
shrinkages you have.
I’m sorry, I can’t offer any tips on the brittle wax. Perhaps it
getting old, was stored in the open a long time or got heated way
too hot. (just speculation…)
Let us know how the Ditto Clear works for you. I’d like to know.