I have recieved enquiries regarding the use of "fat wood" as a tinder in 18th century fire lighting. The original term for this wood from the pine tree was "candlewood", & it can not be used as a tinder for use with flint & steel. It can however be used as kindling.
Another enquirie referred to no documentation found on the use of "candlewood" for fire lighting. Firstly this could be because the wrong name, fat wood, was used in the search, & secondly it seems that candlewood was more popular used as a candle for light rather than using it for kindling in a fire. However, that does not mean that someone did not use candlewood as a kindling in fire lighting in the 18th century. Certainly its use for lighting (candle) was known in the 17th century.
"They are such candles as the Indians commonly use, having no other, and they are nothing else but the wood of the pine tree, cloven in two little slices, something thin, which are so full of the moysture of turpentine and pitch that they burne as cleere as a torch."
Rev. Mr. Higginson. 1633.
"Out of these Pines is gotten the Candlewood that is much spoke of, which may serve as a shift among poore folks, but I cannot commend it for singular good, because it droppeth a pitchy kind of substance where it stands."
Wood, _New England's Prospect. 1642.