Cracks in floor boards fillers?

[shad]

Hello, I'm in the process of building the Jack Sobon house. I used 2"x6" douglass fur for the upstairs subfloor but now I'm considering just finishing this instead of adding another layer of hardwood. Some of it shrank up leaving 1/8 to 3/16 cracks.
What can I use to fill these cracks before I finish the floors?

[shinnlinger]

why do you need to fill them???  Old timers would cram hemp rope in the cracks

[shad]

I need to fill them to keep dust from filtering thru. Hemp rope is a good idea.
Ship builders used rope and pine tar to waterproof decks I read somewhere.
Can you still buy pine tar?

[tyb525]

You don't need the pine tar unless you're wanting to hold water with the floor, some oakum (hemp fiber), hemp rope, or spagnum moss should work fine. You'll want something flexible to still allow the boards to expand and contract.

[shad]

Any thoughts on a natural low VOC finish? I was thinking about raw linseed oil but read it takes a long time to dry and turns black after several years.

[tyb525]

Walnut oil, although it doesn't form as much of a thick hard finish like a varnish would. It will penetrate the wood though and bring out the grain.

[shinnlinger]

I used a product called"hard wax oil"on my white pine floors but was most pleased with tung oil covered with varnish

[beenthere]

tyb525
Do you have a good source/brand that you use?

I notice it runs about $14 for 16 oz. 

[tyb525]

I use mahoneys, I've never used it on a floor, just on furniture, cutting boards, and bowls, however I think it would work for floors. It's easy to repair.

I didn't realize how expensive it was though, looks like almost twice the price of tung oil. Maybe someone knows of a bulk/wholesale supplier? Otherwise, it looks like there are other alternatives for much cheaper.