Nitic / Aquafortic

[bob in the woods]

The reason for using linseed oil etc before heating is to  protect the wood from burning...or so I was told
Prevents scorching of carving etc.

[Eric Kettenburg]

All depends upon the level of heat.  People heating with a torch may still find this method of heating prone to scorching, regardless of what is on the stock. 

Stocks treated with oil prior to heating are also, to my mind, altering the chemical reaction as most linseed oils are acidic in pH and furthermore may or may not possess various other chemicals, including lead.  Stocks treated with oil prior to heating tend to darken considerably over time and at a faster rate.  This has been my experience anyway.

[jerrywh]

 Water may be a great conductor of heat up to 212° but that's it. I don't think your going to change the color much at 212°. All this is nitty gritty you have to heat it until it gets to the desired color whatever that temp is.