Reducing technique (the Shrink-Ray!)

Alex Dumas · Post by **Alex Dumas** » Sun Aug 02, 2009 10:18 pm

I have been reducing kit parts for my current project (the Swift from Space 1999) and some of you have asked for my recipy so I wrote a quick article, here it is

http://scihighmodels.com/howto_shrink.html

DennisH · Post by **DennisH** » Sun Aug 02, 2009 11:11 pm

Thank You!

I recall someone had a series of formulas posted here a while ago, but the thread must have dropped off the boards, 'cuz I couldn't find it when I went looking for it recently.

Mighty fine of you!

Dennis

Migmaker · Post by **Migmaker** » Mon Aug 03, 2009 4:26 pm

I see these are open cavity molds, same work for 2 part molds?
Will

Alex Dumas · Post by **Alex Dumas** » Mon Aug 03, 2009 5:00 pm

Migmaker wrote:I see these are open cavity molds, same work for 2 part molds?
Will

I haven't tried 2 parts molds but it should work.

Wug · Post by **Wug** » Tue Aug 04, 2009 12:58 am

Thanks,

That's remarkable.

Migmaker · Post by **Migmaker** » Tue Aug 04, 2009 1:03 am

honestly, I've been thinking about this and come to the conclusion that I don't think it will work. This is mainly because in a two part mold, you will have a different volume of RTV back side verses the front, So with that in mind, my best estimate is this will only work for single open cavity molds.
I could be wrong, but I think you will end up with different mold shrinkage rates because of this. I hope I'm wrong though...
Will

DennisH · Post by **DennisH** » Tue Aug 04, 2009 8:09 am

Will wrote:

honestly, I've been thinking about this and come to the conclusion that I don't think it will work. This is mainly because in a two part mold, you will have a different volume of RTV back side verses the front, So with that in mind, my best estimate is this will only work for single open cavity molds.
I could be wrong, but I think you will end up with different mold shrinkage rates because of this. I hope I'm wrong though...

What if the mold was poured as one piece and opened using the jeweler's cut method? It would take some skill and patience and might not work for everything, but could have some possibilities???

Just thinking out loud.

Dennis

Migmaker · Post by **Migmaker** » Tue Aug 04, 2009 8:50 am

worth a try!...guess I can run some small tests... I've always only done the single pours though myself....I have however, used this little trick for many years so know the process well..
Cheers,
Will

Alex Dumas · Post by **Alex Dumas** » Tue Aug 04, 2009 9:28 pm

Migmaker wrote:honestly, I've been thinking about this and come to the conclusion that I don't think it will work. This is mainly because in a two part mold, you will have a different volume of RTV back side verses the front, So with that in mind, my best estimate is this will only work for single open cavity molds.
I could be wrong, but I think you will end up with different mold shrinkage rates because of this. I hope I'm wrong though...
Will

I don't think volume matters here. Both mold parts will shrink evenly (loose the same mass ratio) so if they fitted together before shrinking they should still fit correctly after. Still, I haven't tried it myself so I may be wrong...

Migmaker · Post by **Migmaker** » Tue Aug 04, 2009 9:33 pm

right i just meant that there could be issues since the front may contain mor rtv then the back, hope I am wrong though...
Will

Chacal · Post by **Chacal** » Wed Aug 05, 2009 10:05 am

This is one of those things that can only be settled by practical experiments.