Neon tubes resting on styrofoam- OK idea?

One of my neon signs has neon tubes bent into a grid backlighting the sign. Originally the tubes rested on plastic that was hollow underneath. The plastic has long since disintegrated. Was wondering if insulation or packaging type insulation foam would be a good replacement. I’m assuming the tubes don’t really care if they get hot, but I was wondering if I needed to worry about the foam melting or decomposing in this application. The tubes get hot to the touch but not so hot I burn myself by touching them.

Styrofoam insulation has an ignition point of 100ºC (212ºF) – same as boiling water. Your neon tubes should not get that hot. However, once ignited, it is a combustion accelerant, so very dangerous in a fire.

I’d look at something else, or covering it with a more fire-resistant material like the metalized reflectixs insulation/vapor barrier sheets. Or even just a plain sheet of tin.

That ignition point is way too low.
This says 491°C.

Still, I wouldn’t do it. I would use standoffs designed to support neon - your local sign shop should carry them, or you can buy them on ebay.

One needs to be clear what substance one has in mind when talking about “styrofoam”. There are several different materials commonly (and sometimes incorrectly) called by this name. The name is a trademark by Dow for a particular material, but it’s colloquially used for other things too.

The true styrofoam (as I’ve always known it) is that hard crunchy stuff that grade-school children use, to make Christmas and Hanukkah ornaments, which we then spread with white glue and glitter. I believe that substance is the thermal insulator mentioned in the first paragraph of this Wiki page.

(If that’s a thermal insulator, the implication seems to be that it’s safe for the usage that the OP envisions. I wouldn’t expect something called a thermal insulator to melt or catch fire too easily.)

More modernly, the term has become common, but often refers to that softer, more “rubbery” foam commonly seen in fast-food packaging and soft-drink cups. That doesn’t seem to be the kind of stuff I would want to use for thermal insulation.

(IANA engineer, so correct this if wrong, but…)

In the case of styrofoam that may be the case, but I think it would be dangerous to generalize from that. Thermal conductivity is not the same thing as ignition temperature, and if you look at the table on this page (first two columns), the correlation isn’t terribly high.

As real-world examples, some building insulation meant to keep buildings warmer or cooler is dangerously flammable and must be treated with flame retardants. They’re good insulators because of the air trapped within their structure, but they can still catch fire and burn when exposed to sufficiently hot temperatures.

I’m thinking of the stuff used for insulating buildings.

I have no tools for working tin, and I’m afraid of using anything metal due to conductance and capacitance.

Since the neon originally rested on plastic backing, I’d have to drill a bunch of holes to mount standard tube supports but it is a possibility.

Would making your own moldable plastic stand-offs work?

This one required you heat it up to form, and you can do so repeatedly:

This one cures in air sort of like bathtub silicone:

You could also just make a big blob out of bathtub silicone sealant and carve it to suit. Might not be rigid enough, but it’s hard to set fire to once cured.