Re: Sunshine Models


ljack70117@...
 

If you use Dow Corning J RTV rubber and leave the pattern in the mold for 72 hours, there will be no shrinking. But one draw back is you need a vacuum pump and chamber to work with the J.
Thank you
Larry Jackman

On Thursday, September 18, 2003, at 12:14 PM, Andy Carlson wrote:

Actually Paul, you get virtually equal quality by
casting a part from a previous generation of casting.
Did you know that most of Al's and Martin's kits are
composed of 2nd and often 3rd generation castings.
Think about a boxcar side-both are identical, and I
don't know why a Mfr. would make 2 identical sides
just to supply us with 1st generation castings. Even
parts which are used singularly in a kit are 2nd
generation castings due to the building of "Family
Molds" for the production process.

RTV mold making rubber is so good at reproducing
detail, that "MEK Shine" will show on the RTV mold
surface. Also, the good resins will pick up all of the
detail of the mold, so that it gets real difficult to
tell 3rd generation castings from 1st. Of course there
is some shrinkage with each subsequent generation, a
trait the pattern makers realize and make
accommodations.
-Andy Carlson

--- cobrapsl@... wrote:
.... As for casting a part from a resin part, you
don't get much
quality at the end of the process.

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