For your Condensation Cure Silicone Rubber, i was wondering if theres any reason why I wouldnt be able to mix in Fillite poweder to bulk up the main body of  my mould and stiffen its outer walls with?

Looking at this guide https://davidneat.wordpress.com/tag/adding-fillite-to-silicone/ it suggests you can use fillite to bulk up silicone at the cost of stiffness... The reason im considering this is because my mould im looking to make is actually a little larger than i expected and im not sure I have enough silicone to make it now. However ive ran out of money and need to try and extend the mould. 

I'm thinking I can mix up my silicone batch, pour say half the batch on my design and let that get all the details. then quickly mix in the fillte into the remainder and poor that on top of the unmixed silicone.

The stiffness would actually be helpful as I cant make a big mould the stiffness would help with keeping the mould shape true.

Ive ordered some fillite (its really cheap) but i just wanted to be certain with you guys that it shouldnt cause any real trouble? like inhibiting the cure or not "bonding?" even though it seemed to in that guide. 

Any help would be appreciated. 
Thanks
Stay safe.
Simon

Hi Simon,

Adding Fillite to our CS25 RTV silicone is not something we've tested and so I'm unable to give a definitive answer on whether there would be any incompatibility. However, Fillite is a inert material and there's nothing in its make-up that would suggest to me that it would inhibit the cure of the CS25. As for the effect on the behaviour of the silicone, I'd expect something along the lines of what the guide you linked to suggests.

Another option when you're producing large silicone moulds, and the technique that is most widely used in casting studios, would be to create a 'glove mould' where you have a thin-wall silicone surface to your mould and then the structure, shape and strength is provided by a rough-and-ready fibreglass 'jacket'. Fibreglass itself (just GP polyester resin and chopped strand mat) is very inexpensive and will product a very strong shape to the mould, making it possible to produce very large 'silicone moulds' whilst keeping the amount of silicone required to a minimum. Typically, using a glove moulding process the silicone might only be between 5 and 10mm thick. I appreciate that it's more complex process and for the project you're working on right now it might well be best to just push on with your silicone and fillite solution but I thought it might be helpful for you in the future to consider the glove moulding process if you need to make large silicone moulds in the future.

I wish you all the best with it; please let us know how you get on.

Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

+x

 

Matt (Staff) - 5/14/2020 7:33:36 AM

Hi Simon,

Adding Fillite to our CS25 RTV silicone is not something we've tested and so I'm unable to give a definitive answer on whether there would be any incompatibility. However, Fillite is a inert material and there's nothing in its make-up that would suggest to me that it would inhibit the cure of the CS25. As for the effect on the behaviour of the silicone, I'd expect something along the lines of what the guide you linked to suggests.

Another option when you're producing large silicone moulds, and the technique that is most widely used in casting studios, would be to create a 'glove mould' where you have a thin-wall silicone surface to your mould and then the structure, shape and strength is provided by a rough-and-ready fibreglass 'jacket'. Fibreglass itself (just GP polyester resin and chopped strand mat) is very inexpensive and will product a very strong shape to the mould, making it possible to produce very large 'silicone moulds' whilst keeping the amount of silicone required to a minimum. Typically, using a glove moulding process the silicone might only be between 5 and 10mm thick. I appreciate that it's more complex process and for the project you're working on right now it might well be best to just push on with your silicone and fillite solution but I thought it might be helpful for you in the future to consider the glove moulding process if you need to make large silicone moulds in the future.

I wish you all the best with it; please let us know how you get on.

Matt

Hi Matt,  thanks for the quick reply.  I completely forgot about glove moulds like that.  I had considered a similar  idea using latex and plaster Paris...  But I think I read that latex wouldnt hold up with multiple pulls.  
The part I'm casting (multiple parts one mould) takes up roughly 10 inches square...  Maybe a foot... I'm going to be setting up an injection moulded layout, and syringe the resin in from one end. 

I'll post something in the forum when it's done.. 

Again thank you for your help.
Stay safe
Simon