Xjyuk

Tieflings are routinely captured and imprisoned. Those that are compliant enough are sent out and used to hunt other tieflings, but not before having their horns dipped in molten tin as a way of identifying their agents.

My question is whether or not dipping a horn in tin would actually result in a shiny tin coating on the horn or if it would just burn the horn and slough off without adhering to it. This is assuming the horn is similar in composition to a goat or rams horn.

Tin has a melting point of 231.93°C. Brief exposure to this might not char a horn, depending on the nature of the horn. If the horn is relatively thermally conductive then it might well not char, or not much. Especially considering that the tin will tend to stop any oxygen being available and so slowing the char process.

Some types of solder are alloys of tin and various other materials. Some types of solder have melting points as low as 90°C. These are usually less shiny than pure tin. It's possible that, with some tweaking, a brightly shiny form could be made that also had a relatively low melting point. There would need to be some development effort to get something that looked good but didn't simply abrade off in a couple days. Maybe the keepers of these critters care about not poisoning them, so they make an effort to select less toxic materials.

The thing is, horn isn't typically dead and un-growing. It's usually much more like fingernails. Think of hair growing, or a horse's hooves. They typically continue growing because they are expected to be abraded, broken, etc. Some species will shed them on a yearly cycle, and regrow them, possibly at rutting season or some such. Some species will be constantly growing their horns, with new material appearing at the base similar to finger nails or hooves.

So it means that the dip will probably need to be replaced on a regular basis. Depending on exactly how the horns grow it might only be once per year. Or it might require a process similar to "touching up the roots" for people that color their hair. There will also need to be touch-ups if the individual gets into some rough situation and abrades off the coating.

Wheezing off another answer: Probably the horn needs some prep before coating. Certainly it will need to be cleaned. Maybe it needs to be sand-papered, or abraded. Or possibly it needs to be chemically treated first to give the surface a nature that will accept the coating. This would all be part of the ritual.

Further edit: The temperature of the molten metal is certainly going to be enough to harm the fleshy parts of the Tiefling. Even if one of the very low temperature alloys was used. Possibly you are going to want some kind of wrap or ring or something around the base of the horn. This will cover the last small portion that would not actually get dipped. It could be of the same metal or cloth or leather or some other material. You could play a lot of symbolic games with that, it being an obvious symbol of being bound. The ring color could indicate status or rank or some such.

Tin melts at about 450 F (if pure, possibly lower if alloyed -- for instance, Wood's Metal melts in water below boiling). If the horn isn't kept in the liquid longer than needed, the horn wouldn't char (nor would the living core be harmed, because horn is a relatively poor conductor of heat). However, whether tin or an alloy would stick to horn is another question entirely.

One possible way to make this work would be to drill a small hole near the tip of the horn and put a brass or steel rivet in the hole; the tin would adhere to the metal and lock the coating of tin in place on the horn, even if it doesn't adhere to the material itself.

The coating would also be relatively fragile (tin is quite soft, and the low-melting alloys not much harder), so would need to be reapplied periodically, but a simple re-dip should do the job as long as the horn itself hasn't worn down or been broken short enough to lose the rivet.

Tin melts at 231 degrees C and horn starts to char at around 350 C. So probably yes.

But it may also help (or hinder) to soak the horn in something first which may aid the transition and potentially make the tin 'freeze' in place (or just stick) more easily.

Scoring the horn or making holes through it might also help.

You have two problems here:

1. ability of the horn of resisting the heat of the molten tin (above
   231 C, melting point of tin)


2. wettability of the molten tin on the horn

For 1, the fact that you are dipping the horns into the molten tin is already a problem: you will the whole mass of molten metal transferring heat, thus increasing the chances of heat damaging the horn. It would be better if you sprayed it on the horn.

For 2, I cannot find any specific study. For what I have experienced with molten tin, it's not that good at wetting other (metal) surfaces, so it is also hard to have it stitch to something. If this is transferable to horns, it's hard to have them coated.