Introduction: Working With Foam: Tips and Tricks - Smoothing Seams

About: A wellington based cosplayer and propmaker well versed in foamsmithing and creating fantastic weapons, accessories, clothes and armours from the medium of foam. Running weekly Tips and Tricks posts and sharin…

As we catch up with the weekly posts, this instructable looks at the techniques used to smooth those inevitable seams and gaps in our foam props and armour or other foam projects.

These instructables are designed to be simple and informative, and the skills can be transfered easily across to other mediums. If you have any questions about the tips or any suggestions or comments on tips you'd like to see, I'd be very interested in hearing them.

Step 1: What You Will Need

- Your Base Shape/ Prop

- A Knife, Spoon or Metal Flat Edge

- Water

- High Grit Sandpaper

- A Polyfiller/ Decorator's Caulk Filling Compound

- Your Finger

Step 2: Apply the Filler

Using your knife, take a small amount of your filler and apply it to your seem, pushing right in. Don't worry if there is slightly too much, just feather it out away from the seam.

When looking at what filling compound to use, bare in mind whether the area is likely to be subject to a lot of flexing or if its a solid build. This will determine what filler to use. Generally you should use something like a decorator's caulk as this allows a bit of flex, but remains completely sand-able. If you need more flexibility then you should consider a sealant like quik-seal which is a paint-able mastic sealant. It has more flex but you cant sand it.

Step 3: Smooth It All Out

Before the filler dries, wet your finger slightly and then gently feather out the filler you have just applied.

This will help make the joint as seamless as possible.

Step 4: Sanding

Once the filler has dried, take some high grit sand paper, (about 400 -800), and whilst sanding in a circular motion, gently smooth out the filler across the seam.

Keep running your finger lightly over the joint to feel for any imperfections or raised edges.If you come across any after sanding, rinse and repeat until you cant feel the seam any more.