Lego casting mold question

[wing_nut]

I've read many times about using Legos to make the form to make a casting mold. So i gave it a try but now have a question I hope someone that uses this method can answer. How do you keep the liquid rubber from oozing out from underneath?

[fightnjoe]

i am not the most experienced at it but i will tape the legos (i use larger block) and then press the putty into the corners. when i do the second set i do the same. form with the legos and then tape it off.



joe

[sabre]

I don't know if you've seen these clips already WingNut, it's an 8 part tutorial on Mold Making and Resin Casting Your Own Sculpted Miniatures.

[paulh]

To be honest the fit of lego bricks is so tight I wouldn't have thought you would get much (if any)leakage- but thats just speaking as a father who gets asked to help construct/deconstruct lego on an occasional basis no experience (yet) using it as a mould case.
P

[Deleted]

I've used it a few times in the past for casting extra 1/72 weapons for my aircraft builds around 15 years ago.

i found that if you smear the inside with petroleum jelly after you've built the 'box' it stops leakage (you're right, there isn't much) but more importantly you can get the mould out of the box and the rubber doesn't stick the bricks together.
Maybe today's casting rubber or silicones are easier to work with but that's where I'd start 

[venom1]

Hey Marc,

I take it you are talking about the underside of the "dam" after you have made it?

I do a bit of casting, and I use a floor tile to cast on. I build a dam around the part with Lego on the floor tile (makes for a nice hard, smooth surface), then seal the bottom edge with modelling clay. This has a twofold effect of both sealing the Lego to stop silicone coming out, and also stops the Lego from moving around, which is especially important if you are only doing a one piece mold.

I also spray the inside of the mold with Rocket Release (an aerosol based release agent) before pouring which helps in the removal of the Lego from the mold.

I am actually planning to do a couple of blogs on resin casting at some stage, looks like I should make it sooner rather than later!

Hope this helps!

Cheers,

Sam