Hello. I would greatly appreciate advice for making moulds for picture frames. As you see in the photo attached to this post, I have a master that is made of acrylic. There are four parallel sides and a top lip that is perpendicular to the sides. I was thinking about casting it so that the top of the lip is exposed. this way i only need a one part mould. Gravity will level whatever material is poured into the mould to create a flat surface. But perhaps there are problems with this method that I am not aware of?

Hi Michael,

Interesting project! I’m glad you’ve come and asked thequestion before pouring resin over the acrylic master! Your concept for themould pouring method is fine, you will just need to change the materials youare planning to use a little.

I would advise making the mould from addition cure silicone rubber. This is because your pattern has parallel sides there would be almostno chance of separating them, silicone on the other hand will simply peel awayfrom the MDF barriers and acrylic with no need for release agent. This would alsobe true for casting the parts themselves, a rigid mould for casting is fairlyuncommon – you would face the same release issue as you would with thepattern/mould.

On another note you mentioned ‘epoxy in styrene’ this isprobably polyester in styrene and not epoxy resin. I would avoid using styrene resinsystem with acrylic as it is liable to attack the plastic and fuse permanently.

You also mentioned that you wanted to potentially castsilicone parts; this would be the only material that would need a release agentto be cast into the silicone mould as silicone with stick to itself. A verysimple and reliable release agent for this is petroleum jelly (Vaseline). Otherthat silicone all of the other materials will release from silicone with noproblems.

I hope this helps, good luck with your project.

Paul Statham
Easy Composites / Carbon Mods - Technical

Hi Paul. Thank you for the details. I will be taking your advice and using addition silicone rubber for the moulds. 

hope to hear from you one more time before i make a purchase. much appreciated.

Hi Michael,

Sorry Paul's not got back to you on this, we have a training course on this week and he takes the course and therefore doesn't get chance to check back in on the forum. I'm sure I can answer your questions....

1. should i put the master into my mdf mould frame before pouring in the silicone or after? Does it matter which method?

It doesn't make a huge amount of different. I think the more common practice would be to position the master in place and then pour the Addition Cure Silicone Rubber around it. Don't forget to secure the master down, I don't think acrylic is lower density that silicone (which would cause it to float) but it's quite close and so not worth risking.

2. i love the look of this art that was made in the 60's by Eva Hesse, actually, this brownish yellow stuff is what originally attracted me, many years ago to resin casting. Do you possibly know what this is exactly, what materials create this color and where I can find this material?

It's difficult to say exactly what Eva's pieces are made from but certainly the appearance of them is very similar to the appearance of a cured sample of GP Laminating Resin. Once cured, the GP resin has that slight translucent brown tint and might be very close without any modification, however if you did want to tweak the colour then our box of 10 Translucent Tinting Pigments includes a 'Burnt Sienna' colour which is a really nice caramel brown colour.

It would also be possible to recreate a colour and appearance like this using a clear resin such as our Water Clear Polyester Casting Resin or even our Water Clear Polyurethane Casting Resin (although really this second resin would need degassing to remove air bubbles) and then just tinting them using the tinting pigments I linked to earlier.

3. there are little chips and dings in my master that need to be filled with putty and sanded smooth. what do you recommend for this?

If you're using silicone to make the mould then it won't really stick to anything so you can, effectively, use anything you want to patch-up your master. Polyester bodyfiller might be any option or, if you're careful, you might find that our yellow filleting wax, which can be shaped and smoothed incredibly easily, would be a simple option.

I hope this helps and look forward to seeing your finished pieces

Best regards, Matt


Matt Statham
Easy Composites / Carbon Mods - Technical Sales