Reusing hardened silicone?

[AlexM]

Hello there,

 

I'm currently making my first experiences with silicone moulding and resin casting. Yesterday I made my first silicon mould - and totally messed it up, as the object I wanted to mold detachted from the ground and than was then swimming within the silicone while curing . Seems to be a really learning-by-doing-process...

 

No I have an unusable lump of hardened silicone which is annoying considering the high price of silicone  

 

I wonder if I could cut the failed mould into small pieces and reuse them when making a new (hopefully successful) mould by mixing the small hardened pieces with fresh (two-component) liquid silicone. Will the liquid silicon "merge" with the small parts, so that I get a homogeneous mass at the end?

 

Cheers

Alex

 

[BiggTim]

I've had that happen, too. I'd say yes, the pieces should bond well with the new stuff, but I can't guarantee that they will align as well you're hoping so the best I can say is to give it a shot. What do you have to lose, right? If works, then you saved a bit of mold rubber. If it doesn't, then you wasted some. All of who've tried resin casting have wasted a bunch learning the process.

 

Tim

[D Bellis]

I wonder if I could cut the failed mould into small pieces and reuse them when making a new (hopefully successful) mould by mixing the small hardened pieces with fresh (two-component) liquid silicone. Will the liquid silicon "merge" with the small parts, so that I get a homogeneous mass at the end?

Yes, I do this frequently.

 

Make sure to wash any release agent off of the mold being scrapped before using chunks of it as 'filler', and they will become one with the new molds.

 

HTH,

D

Edited August 2, 2015 by D Bellis

[AlexM]

Thank you guys! Then all is not lost

[phasephantomphixer]

Also, try to keep the recycled hunks away from the item as it can leave surface marks when you cast.

[AlexM]

Also, try to keep the recycled hunks away from the item as it can leave surface marks when you cast.

 

Thanks for the advice!

[stevegallacci]

Been bulking up molds with chopped old material for years. Yes to keeping the old stuff away from the pattern area also as the new mold material may differentually adjust as it cures. Not nessisarily shrink, but may do some kind of dimensional dance, and there may be some distortion. And along with that is the matter of sizing your chunks. Smaller is better. However, for some mold shapes, you can, in effect, re-line a fresh impression into a bulky mold. Another thing with old material mixed with new stuff, the new material may cure slower if you have a lot mixed in. HOWEVER, the clear-ish platinum silicon mold material will not adhere to itself, so doing a mold in more than one pour with some setting time between them won't work, nor can you recycle old material into a new mold.

[wunwinglow]

Also, if you do try to reuse old moulds, try not to include any material from the cavity. because the isocyanates absorbed into the rubber will inhibit the cure of the fresh rubber.

 

We don't bother trying to reuse old moulds, the time it takes to hack up old moulds is much more valuable making new moulds from fresh material. Also, buying rubber in large quantities brings the price down even further.

[AlexM]

I experienced that cutting silicone into small pieces with the knife is very tiring. Is there a way to chop/grind it up?

[D Bellis]

I experienced that cutting silicone into small pieces with the knife is very tiring. Is there a way to chop/grind it up?

Much to my wife's dismay, I commandeered one of these from her kitchen for that task last time, and it made the job easy:

http://www.amazon.com/Ulu-Company-Knife-Wood-Handle/dp/B004CUO4MO/ref=sr_1_6

 

HTH,

D

[AlexM]

Hi there,

 

I recently saw this video on youtube:

 

https://www.youtube.com/watch?v=aZ_k895KzdI

 

I gave it a try and ordered the cheapest hand driven meat grinder on Ebay for just 10 € with free shipping. The frist attemp was quite promising. This is the result of an evening of work.

 

 

 

 

The size of the grinded silicone varies, from rather large to very small pieces. I think that repeating the process would result into even finer grinded parts.

I have no weighing scale at hand, but I guess the value of the grinded silicone is at least 10 €

[Mustang JBB]

I experienced that cutting silicone into small pieces with the knife is very tiring. Is there a way to chop/grind it up?

If your old molds are small, maybe a coarse cheese grater.

[I R Tubes]

I've had mixed results trying to reuse fully cured silicone. Small pieces can be embedded in fresh silicone as a filler to reduce waste, but they won't chemically fuse into a single homogeneous block. That means the mold can end up with weak points or visible seams, especially if those pieces are close to the mold surface. If the failed mold is large, using chopped cured silicone as a core with a layer of fresh silicone around the cavity can be a practical way to save material. For critical molds where surface finish and detail matter, though, starting with fresh silicone usually gives the most reliable results. Also, securing the master firmly before pouring—using CA glue, double-sided tape, or a small amount of hot glue—helps prevent it from floating during curing.

[RCPlym]

If you use platinum cure RTV, don't recycle old into new. You will end up with uncured silicone around every old piece you put into it, resulting in a very unstable mould.