Clear Finish for Blue Pine Mantel?

[Cory Bednarz]

I've got a 4" x 12" x 8' slab of blue pine (or beetle kill pine) with bug tracks and all that I want to cut down to about 5.5' and use as a mantel over a new gas insert fireplace we're having installed. I want to make sure I use a finish that will be heat resistant enough so that I don't have any bubbling issues. I will be mounting the mantel at the recommended distance per the insert specs (in this case 21" above top of fireplace) so firecode wise I'll be fine but I'm sure the bottom of it will likely get warm. I don't have much experience with woodworking but I've been reading some and oil based finishes seem to be best for heat resistance but I really like the look of raw blue pine and I want to avoid it ambering as much as I can. I've seen a blue pine cutting board that was really ambered and I don't want my mantel to look like that if I can help it.

Is there an oil based finish out there that has minimal ambering or conversely is there a water based finish that has good enough heat resistance to use without potentially bubbling? I'm going to be putting in the insert before the mantel so I plan on taking a test board that's 12" wide and clamping it to the top of the masonry (the top course of brick sticks out enough to do this) so I can see just what kind of temps I'd be dealing with. Not sure what the temp threshold is for water based products.


Secondary question is that this slab has a lot of bug tracks, do I need to do anything special with those when finishing? I like the look of them but if I'm wiping on a finish are those tracks going to fill with liquid and never fully cure? I'd rather not go the route of filling them with epoxy if I don't have to, there are a lot of tracks so it'd be a bunch to fill.

[John TenEyck]

If you meet the code requirements for mounting the mantel my guess is that waterborne finishes will be just fine. If you use a product with a flat or matte sheen it will look like no finish at all yet will be protected. General Finishes High Performance waterborne is brushable or sprayable and has a UV package that will keep it from yellowing over time. Sherwin Williams' KemAqua+ is sprayable only but has a dual UV package that will prevent UV damage to both the finish and the underlying wood. No UV package lasts forever but they will prevent yellowing for many years unless it gets baked in the sun daily.

If you can spray the finish you shouldn't have problems with it oozing back out of the holes. If you brush it then just do one side at a time face up, if possible, to prevent the finish from draining back out.

John