SilentMODs: UV-Reactive Pumpkin Heads

It’s been a while since I’ve posted my YouTube videos on this weblog, and there’s no better time to do so than now. Check out the SilentMode.tv YouTube channel if you haven’t visited before, and be sure to “like” the videos you’ve enjoyed watching.

This edition of SilentMODs just happens to exclusively use materials from Smooth-On. They produce a number of easy to use products for creating moulds and castings.

Decorations for Hallowe’en.

It was just over a week before Hallowe’en 2017, and I had to act very quickly if I wanted to produce anything. Building an MOC was out of the question as I’ve been busy sorting through my parts collection, and I have much less building space than before.

The idea for the “pumpkin” heads came when seeing the first few Hallowe’en creations over on social media. I’d bought the large minifigure head – which came from one of those large minifigure clocks or torches – at a meetup a couple of months ago for a similar purpose.

Choices of materials.

The time constraint was the primary reason for using Smooth-On’s Dragon Skin 10 NV silicone rubber for the moulds. I’d used a similar third-party silicone rubber in my older SilentMODs videos, which cured in just over an hour. Best of all, the “NV” in Dragon Skin 10 NV stands for “no vacuum”, meaning I didn’t have to use a vacuum chamber to remove air bubbles.

I had the option of making the heads glow in the dark, but instead I wanted to make them UV-reactive. This was accomplished with a trial pack of Ignite pigments, which react significantly to UV light.

Smooth Cast 65D is Smooth-On’s offering for rotocasting, or creating hollow castings. While I could have opted to use any of their other resins, I wanted to produce as many castings as possible from one batch. Smooth Cast 65D also has a short pot life of 2½ minutes and cures in 15 minutes.

“Pumpkin” colours.

I only discovered yesterday that Smooth-On’s So Strong pigment line actually includes Orange, but there isn’t an Orange in their trial pack. As a result, I couldn’t get the orange colour I wanted when mixing the other So Strong pigments. I guess the silver lining was that I could produce a variety of shades, resembling different types of “pumpkin”.

Smooth Cast 65D cures to a white colour, which lightens any pigments added. As far as I know there isn’t a colour matching solution for rotocasting.

Smooth-On also produces UVO pigments, which are designed to resist UV light. I would definitely recommend using So Strong with Ignite, solely because UVO pigments produce opaque castings.

Faux cutouts.

My Silhouette Portrait cutter was brought out of its own retirement to produce the decorations.

You might recognise the standard Jack-o-Lanterns as interpretations of official minifigure heads. I also included a few deliberately chosen “other” design, just to demonstrate that pumpkins don’t have to be Jack-o-Lanterns.

The end result…

SilentMODs: UV-Reactive "Pumpkin" Heads.

I was fairly pleased with how these heads came out. The UV effect was definitely superior when using So Strong pigments versus UVO – I just wish I had the Orange So Strong pigment.

Along the way I’d gotten the ratio of part A to B wrong, when measuring the Smooth Cast 65D by volume. Smaller quantities should really be measured by weight, due to bulk mixing cups catering to large measurements. As a result, many of the heads were soft and slightly sticky.

For some reason the vinyl cut designs were slightly larger than they should have been. The vinyl cutter also had trouble with small details, so the custom designs had little pieces missing.

In conclusion…

The UV reaction was a nice-to-have feature, but to make the most of it would require a setup to be able to show off the glowing effect. These heads would have worked just as well if they were coloured orange, or any realistic pumpkin shade.

Let me know what you think of these heads by leaving a comment below!