Home-made diffuser caps for LEDs

The first catctus (Frankencactus) turned out surprisingly well, in the sense of adding coziness of the space. Despite it’s technical flaws, it was appreciated by visitors and flatmates. Great success!

Since the motivation for building another cactus was high, I wanted to become diffuser-independentTM. Huh? Well, the original “diffuser caps” (photo below) were limited, since they were scavenged from some old christmas lights and I could not find anything similar on the internet. Weighting between different LED diffusion options, like 3D printing, paper and others, the idea of casting/molding seemed the most fun.

sweater with silicone stains that won't wash off

Silicone mold

There’s a nice overview of silicone mold-making techniques by Steve McDonald in this video. Using an ordinary silicone and soaped water, we formed a “snake” and pressed the original diffusers inside (with their necks sticking out).


  • silicone smells like vinegar, badly. It burns your nose and makes your room disgusting.
  • it sticks to your hands and it takes forever to get rid of it. Tip to self: use gloves!
  • don’t get it on your clothes! Below is a photo of my hoodie, after the washing. Yep, that was embarrasing to explain to my flatmates….

sweater with silicone stains that won't wash off

The mold was dried quickly (approx. 15-20 mins) and looked okay. Rubber-like feeling, not super squishy, but flexible enough to get the original piece out. We filled it using a glue gun, until the glue started pouring out of the hole. We sliced the mold horizontally, to get the pieces out and finally drilled a hole into their necks, for the LEDs. Here are some results:

It took some attempts to get it right, mostly due to awkward glue gun and no constant inflow (I guess). However, it turned out pretty good eventually, it felt like real plastic. One of the questions was whether to slice it on the top (where the necks are) or at the bottom. I did it in the bottom for some reason, but it turned out to be a bad idea since the hot glue was escaping on the bottom while pouring it in. Slicing the mold on the top would probably be better.

Any alternative ideas on diffuser cap making?