This is one of my favorite maker hacks. Learned this as a kid making models.

Step 1: What You Need

Mixing superglue and baking soda creates an opaque, hard, drillable, sandable filler. It also sets up and hardens almost immediately, so you need to plan ahead and work fast.

You need:
Superglue
Baking soda
Brush (optional)

Step 2: Ready, Set...it's Done

Watch the video to see the magic.

I like to use this for repairs. I use a Brush to dust the edge. Put the parts together and apply glue. Once you apply the glue it instantly hardens. I then apply another dusting to renforcement the seam. Allow to cure for an hour or more before sanding, shaping or drilling.

As a filler, tape off area and apply alternate amounts of glue and Baking soda. For thick pieces of filler, allow 10 minutes between layers of 1/4 inch or more.

There is an exothermic reaction and the mix gets hot, so use caution. It is somewhat brittle at this stage. Once it cures it's rock hard.

Step 3: Endless Applications

This can be used for modeling, automotive fixes, boating, crafting...literally, thousands of applications.

Remember, be safe. Use eye protection. Acetone can be used for clean up. Use nail polish remover for getting glue off hands.