Sanding Complex Contours Trick: Mold the Molding!

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Forum topic by Nicholas Hall posted 09-08-2016 06:24 PM 819 views 1 time favorited 0 replies Add to Favorites Watch
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Nicholas Hall

352 posts in 2664 days

09-08-2016 06:24 PM

In a recent crib project I routed a complex moulding with fine detail. I was trying to figure out how to sand a complex molding without messing it up. I poked around on the internet and found that the two most common suggestions were to hand shape hard foam insulation, or use a rotary sanding tool on a drill. I didn’t have either, and neither seemed like an adequate approach (too much time for foam and too coarse for a rotary sanding tool.

I came up with a solution that I haven’t seen elsewhere so I thought I’d post it. I decided that the best way to capture the fine detail of the molding was too actually take a mold of the profile and use that as my sanding block. By golly it works. It probably sounds like a chore, but it only took 5 mins.

I used a product called Instamorph that I got off of amazon for about $6 delivered. It’s a food safe polymer that turns into playdough at 155 degrees F, but hardens like ABS at room temperature. Here are it’s virutes:

- Can be heated in water to soften it (mug of water 1min on high in microwave)
- Can hold detail down to 0.2mm
- Can be reused hundreds of times
- Costs just $6.00 delivered!
- FDA approved food safe

Basically I just heated some water in a small pot. I let it get close to boiling. I dropped in the pellets, they congealed into a blog of soft, squishy plastic (like playdough). I took the blob out of the water, stuck it on the molding, let it cool for a few minutes to harden. Put sandpaper on it, and sanded my molding with a sanding block that perectly matched the profile. Easy peasy. Next time I have a complex countour that I want to sand I’ll just drop it in some hot water and repeat. Apparently you can do it hundreds of times.

I’m totally in love with this stuff now; Once it hardens you need a vise just to bend it. I’m trying to brainstorm other uses for it. This stuff would be like magic for jigs & workholding tricky pieces.

Here are some pics of the process. I didn’t take pics of the crib molding so I just stuck it on a drawer for an example:

Anyhow, this instamorph stuff is fantastic. Is anyone else using this stuff in woodworking? What do you use it for? Any ideas of where it might come in handy?

-- Outside of a dog, a book is a man's best friend. Inside of a dog, it's too dark to read. -Groucho Marx

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