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One of the simplest ways someone can get a piece made for aluminum casting is to make a scratch block. A scratch block is a brick that you carve into to make a mold to pour aluminum into. Whatever you carve needs to be inverted and negative. Up is down (into the block) and right is left on the face of the block.

Carving the bricks is super easy. Grab your fingernails, a screwdriver or any other sharp tool and dig in!

Making the bricks for an event is relatively simple and can be done in about 90 minutes. The bricks need approximately 24 hours to cure and set after they are mixed up and packed into the molds.


  • Scale
  • Some cups.
  • 50 lbs of sand
  • 455g of resin
  • 115g of catalyst.
  • 3 buckets
  • a big drill with a mixing bit.
  • some gloves!

Start by splitting 25 lbs of sand into 2 buckets. Even it out and then form a little divot that we will use to pour the resin into.

Almost fill up one of the cups with some of the resin. Set another cup on the scale and pour the resin from one cup into the other. You want 455g of the resin. Use 2 cups so you have a place to put any excess. Once you have the proper amount, pour half of it into each of the buckets with the sand. Cover it up with a light layer of sand after that and get to mixing! Mix each bucket for a couple of minutes and really work it around. After a couple minutes are up, pour one of the buckets into the empty bucket in order to reach the bottom sand. Do the same for the other bucket. Do this 3 or so times. You will be done when the sand has a consistent color and consistency.

Now that that is done, get your catalyst ready. Close up and put the resin away before you do this! Even a tiny bit of the catalyst will activate the entire container of resin and ruin it. Don't ruin the resin! You need 115g of the catalyst (1/4th of the amount of the resin). Use the same procedure you used to measure out the resin and when you have the right amount, split it up between the two buckets of sand. Go back to mixing! Do the same thing as you did with the resin and mix it and switch buckets 2 or 3 times until things are nice and consistent.

Once this is done, you have the sand you need to pack the molds. Before you pack them, you need to do 2 things. First, coat the molds with a bit of talc or baby powder. You want an even covering over the mold, but don't leave any piles. After that is done, put on some gloves! You do not want to be handling the sand with the resin+catalyst mixture - it will at a minimum irritate your skin. With your newly begloved hands, start packing sand into the molds. You want it to be nice and tightly packed around the surface of the mold. The higher you go, the less you need to be super precise. You do want the surface you will be carving into and pouring onto to be super smooth, so take the most care there. One the bricks are all packed, put them on top of the shelf with the casting supplies by the garage door. Separate them with a piece of cardboard. Leave them for 24 hours to cure.

Once your bricks are done, you can pick up after yourself! Your fellow makers will thank you for putting all of the materials back where you got them, sweeping up any errant sand and cleaning up any other messes that occurred along the way.

After 24 hours have passed, you need to pop the bricks out of their molds. Using a putty knife, go in around the edges and loosen the brick up. Flip the mold over and gently shake the brick out. Be careful not to pick it up and shake it out. If it comes flying out of the mold, it will most likely shatter and you will be sad! Don't be sad! When all of the bricks are out of the molds, stack them up again on top of the casting supplies shelf, separated by some cardboard.

casting/makingscratchblocks.txt · Last modified: 2013/07/12 00:30 by plural