Casting a Drain Stopper

I needed a drain stopper in a pinch — and realized I had what I needed to make one at home

Jeremy Elson, October 2019

We don’t host big parties very often, so Liesl and I were caught unprepared when we needed to chill a lot of beverages by filling our big metal sink with bags of ice. After living in the same place for 11 years we suddenly realized we did not own a drain stopper. Of course, what’s the fun in going to the store? I had all the parts on hand to make one at home.

First, I measured our sink’s drain hole and drew a simple 3D model of a drain stopper in negative: simply a flat disc with a little rectangular handle attached.

I printed the mold in PLA. Printing went quickly because I could use a very low infill; it did not need much strength.

I sprayed some mold-release on the plastic mold, weighed and mixed a batch of silicone rubber and slowly poured it. Pouring the silicone slowly from up high helps to remove air bubbles.

My favorite brand of mold-making products is Smooth-On. They have a comprehensive catalog, but for this project I used one of their most basic silicones - Mold Star 30. You can buy it in small quantities, all the way down to a quart, at Reynolds Advanced Materials. They’ve got variants that are food-safe, that are transparent, that are fast-curing, that can be used against skin…. their catalog is nerd porn!

After letting the silicone cure, I carefully demolded it. It came out beautifully.

Finally, the test: does it hold water? It did! It was sized perfectly and the slight flex of the soft rubber helped it conform to the sides of the drain.

It’s not hard to buy a drain stopper, of course. But there’s something very satisfying to me about fabricating my own custom part with materials I had in the house already. My only regret is that I didn’t engrave a custom “L&J” in it, like I did with the toaster!