For those wondering about the use of muriatic acid, here's a quote from a chemist in lay mens terms.
"The muriatic (AKA HCl AKA Hydrochloric) acid does the sugar version. The burn off concentrates the acid by boiling off water. When concentrated enough it removes "water" from sugars and some other "sap" like stuff leaving an oil behind. Think of it as a black tar if you like. If heated hot enough (quite a low heat actually 150C/300F ish ) the acid will also boil away. So the technique is to gently heat so the acid has a chance to work before it disappears.
Second, The remaining muriatic acid will stop working when cold. It will also dilute itself when cold. I.e It absorbs moisture from the air. And last it will disappear (evaporate / fume) slowly all by itself. Technically speaking it is a gas. What we know as the acid is just the gas in a solution of water.
A quick wash in water, or left for a week, before sealing, is all that is required."
Hope this explains it better than I can.