Re: Sealing a Red Oak Mantle
Cracking is due to uneven drying. The ends dry faster than the rest and has a tendency to split. That's one of the problems using green wood. Normal air drying for a piece 5" thick is usually about 5 years but being over the fireplace it may be faster. The main thing is to seal the ends. Poly, paint, or even paraffin is used when drying lumber. Without knowing the moisture content it is difficult to say if you should seal the whole piece because you will only be sealing 5 sides. It may be better to just seal the ends and wait a few years befor sealing the rest.
Be sure you live your life, because you are a long time dead.-Scottish Proverb