The point is I brought the nail over to a friend's house the other night, he uses a propane tank like that to heat it. It only took around 45-50 seconds to get the nail properly heated with that.
My question is if there's any harm in using a propane torch to heat my nail I'm about to dab on.
For the record my titanium nail is a massive domeless nail. It's as long as a king size sharpie with the slide attached. It takes a lot of heating up.
Here's the butane vs propane torch argument
in my opinion:
A propane torch on low is putting out a similar temperature to a high-end butane torch on high. The "2400F" and "3600F" ratings are maxes under perfect conditions.
You are right that a super-thick TI nail is pretty indestructible.
However, the issue with the propane torch deals with oxidation.
Info pulled from Highly Educated:
Titanium oxide...The hotter you get your titanium the more readily it reacts with the oxygen in the air and subsequently the faster it oxidizes.
A thick oxidation layer on your nail or pad can affect its efficiency. The oxide layer can be removed with an abrasive or a small sharp tool such as a flat head dabber and it is recommended you rinse the titanium after to prevent any of the dust particulates from entering your glass or, more importantly, your body. Unfortunately, rinsing the nail only invites more oxide as torching a wet nail will make it oxidize faster. This is because the oxygen in the water is plentiful and in direct contact with the titanium. Over time a nail head can become so oxidized that it has lost much of its original heat retention capabilities. It takes quite some time for a nail head or pad to become worn enough that it would ever need replacing
TLDR: constantly blasting your nail with a propane torch on HIGH (using the hottest part of the flame, the inner white-blue tip) will cause oxidation to happen much faster, even on a fat nail. However, you could always use the propane torch NOT on max, or NOT use the inner white-blue tip of the flame. In those cases, the temperature is much more comparable to a high-power butane torch.
An oxidized nail doesn't hold its heat well. If you spent $100+ on a nail and want* it to last years, not six months, then aim for gradual heating of the nail with whatever torch you wish. Propane fuel is simply cheaper than refined butane, and there are ways to heat your nail with a propane torch that won't overheat it.