Burning wood with ammonium chloride

There is a method where you use a water solution of ammonium chloride to paint some pattern or write some text on a piece of wood and then blow on it with a heat gun. The result is that the pattern you painted becomes burnt into the wood.


I wonder what could be the mechanism behind how this works?


Here is a video where a guy does that: <https://www.youtube.com/watch?v=zV0zC2qRFxE>




Here is my guess as to what is going on: a solution of ammonium chloride is painted onto the surface of the wood leading to ammonium chloride being absorbed into the surface wood fibres. Ammonium chloride decomposes to ammonia + hydrogen chloride above 340C. Heating with the heat gun achieves this temperature (which is why it takes a while in the video). Either gas (or both) causes darkening of the wood revealing the design.


This seems to be backed up by the explanation here: <https://hackaday.com/2011/05/16/chemical-wood-burning/>


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Heating surface with an application of $\ce{NH4Cl}$ results in the release of gaseous $\ce{HCl}$ and especially $\ce{NH3}$, which [per Wikipedia on ammonia fuming](https://en.wikipedia.org/wiki/Ammonia_fuming), to quote:



> 
> Ammonia fuming is a wood finishing process that darkens wood and brings out the grain pattern. It consists of exposing the wood to fumes from a strong aqueous solution of ammonium hydroxide which reacts with the tannins in the wood. The process works best on white oak because of the high tannin content of this wood. Fumed oak is also called smoked oak.
> 
> 
> 


I trust this helps.


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