How can you know for sure that a keycap is dyesubbed?

[connection]

I've been looking at a few older keycaps, and I'm a bit unsure on how to make sure whether a keycap is dyesubbed or if it's pad printed. On newer keycaps the pad printed always (?) have an extra layer of clear coat over the print, which makes it easy to spot, but I have a few older keyboards without this layer, that I still suspect are pad printed, as the paint has been peeled off. So, is there any nondestructive way of checking what kind of print a keycap has?

[Jocelyn]

Yeah I don't know. Ask Ivan imo, he knows everything

[CommunistWitchDr]

as the paint has been peeled off.

Yeah, that probably isn't dyesub.

[fohat.digs]

To grossly over-simplify, the "sub" part of dye-sublimation means that the dye penetrates into the body of the material rather than being a surface film or layer that can peel off.

The entire surface plane must be ablated farther than the penetration of the dye in order for the image to disappear.

Only rootwyrm can do that.

[rowdy]

Cut it in half with a sharp knife?

[connection]

Thanks for the replies! Yes, peeled off paint probably means pad print, but I have other keyboards where I don't want to try to damage the keys or the print to make sure. I'm struggling to spot any differences between that keyboard that is pad printed, keycaps that I know are dyesubbed, and unknown ones. The keyboard with peeled off print has been in industrial use before, so I'm still not 100 % certain if it's really pad print.

I also know that dyesubbed print disappears after heavy use. My father used to print pens with a dye-sub machine during the early 90's, and on some of these pens that have been heavily used, the print has started to disappear. This machine is a small model, so the print probably wasn't that deep into the plastic as a factory printed keycap would have.

[Hyde]

Pad print usually has a thickness to it, even if it's very small.  Imagine putting sticker on keyboard.

Dye-sub usually will be perfectly flat, since the paint is penetrated into the plastic and become part of it.  But yes dye-sub only penetrated down to a certain degress, so if you physically wear the keycap down beyond that then it will disappear.

[IvanIvanovich]

One of easiest ways is to test if the keycap is PBT. Only dyesub on PBT, not ABS. If it is PBT keycap it is more likely to be dyesub than pad printed. Pad printing is cheaper process, so them using PBT which is generally more expensive material is less likely.

[esoomenona]

You can usually feel or see something for certain types of legends.

Pad printed - feel the bump of the printed legend
Laser etched - feel the indentation of the lasered legend
Doubleshot - see the two interweaved shots from the bottom
Dyesub - can't feel or see anything