Re: Mold Release needed ?

[OS1880]

Trying to make a silicone block mold. I have the ratio's between silicone and catalyst correct. But when I go to remove the master after curing it is stuck to the point the mold tears apart. In a previous thread it was stated use of a mold release or PAM is recommended. Now I take it this is for resin in a silicone mold . But what about in uncured silicone for the mold. Will a release or Pam (which the boss has) affect the uncured silicone. I have tried 3 times with the same results, destroyed molds and the last one split the master clean in half , spent an hour scraping of cured resin to save the master. Any ideas.

[oneslim]

OS1880,

You must use a mold release! Silicone will stick to everything everytime. Check this topic of mine. viewtopic.php?f=59&t=50542

I use the Micro-Mark brush on found here:http://www.micromark.com/RUBBER-TO-RUBB ... ,7507.html

It's very easy to use, and control, the spray can build up too much.

Bob W

[Sean Hert]

Depends on the silicone- sounds like you might need some release- but some pics of your mold geometery might help.

Personally, I NEVER use mold release. It prematurly ages your silicone, shortening mold life.

I've been casting for about 16 years, and the only time I use release is when making multi-part molds. If you are ever pouring silicone on silicone, you must use a release or they will bond to each other.

[OS1880]

it's a simple block mold 7"LX2"wx 1.25"h. with the master set in the center. using a product from Hobbysilicone.com. I have never done this before. I wanted something pretty straightforward. I made one it came out passible. Reading the instructions to the letter with no mention of using a release. The master came out with a little trouble but not like the second one. On the second mold the master was stuck and wouldn't release and tore the details as the master was pulled out it broke in half and most of the details were torn from the silicone and remained on the master. This is why I was wondering about a release and it's effect on uncured silicone.
It is their Firm-128 formula. With a 12 to 16 hrs demold time. And the resin is their MPK70 with a 180 sec gel time.

[Sean Hert]

Now wait- when you say "master" what do you mean? A "master" is the part you use to create the mold- the part you pour silicone over. Quite often masters don't survive the mold-making process.

The part that gets MADE from pouring resin into your silicone mold is a "casting." If you are having trouble removing castings from your silicone, then yes, try a mold release. What part is it you are casting?

[OS1880]

I understand what you are saying , the master is a hull that I want to make a mold of. I tried making another on this time I brushed on some PAM and it came out of the mold with no problem. I then tried casting one and it to came out OK with a little cleaning up it will work. Thanks for your help.

[Steppenrig]

Hi all,

A sort of related question, can Silicone spray (the type used for freeing zippers etc) be used as a release?

Background: I scratchbuilt a hull out of MDF, Balsa, Fibreglass and Filler, but due to impatience on my behalf, the planking was uneven which had follow-on effects of too many low spots, and the use of lots of filler. I ended up with a very heavy hull (about 3 kg for a 1.5 metre hull, which equates to 3/8 of my usable mass for the ship). Doesn't sound like much, but i'm yet to finish the hull so I expect to add more weight.

My plan: considering that this is a hull of my own design, I have lots of artistic license to modify. So; I'm going to use the hull (once it's smoothed) as a plug and lay fibreglass over the plug to create the final hull.

Which takes us back to the release. Will Silcone spray work?

Dave

[OS1880]

I should think it would . I have used it on many things it dries leaving a smooth surface. But I have never used it in any of my silicone molds. What I use on my molds is a Dry Film PTFE lubricant made by LPS.