Maintaining Old Floors
I have 12-inch-wide heart pine floors in my 1870 farm house in northern Virginia. They are beginning to crack along the tongue and groove joints. In places, the varnish is coming off. I am concerned that the floors are not getting enough moisture. What do I "feed" my old floors to keep them from getting brittle and cracking? I need to re-stain areas and protect the wood but I want the color to be even and for the wood to be protected. Until now I have only used Liquid Gold on the floors.

You may be seeing nothing more than nature at work. Among the many amazing characteristics of wood is its ability to absorb and release moisture. In summer, when the relative humidity tends to be high, wood takes in moisture and expands. In winter, when interior air is very dry, wood shrinks.
Wood scientists have a formula that predicts how much a board will change in width, thickness and length as it goes through this continuous cycle. Without getting bogged down in the math, a 12-inch pine board might change ¼ inch in width with seasonal fluctuations in humidity inside your house.
When wood is restrained from moving naturally, it can crack. Or floor boards can be pressed tightly together to form telltale compression ridges where they meet. Maintaining a steady humidity level inside will help minimize the problem, but you can't really stop the process.
Wood doesn't need feeding
Wood does seem to get brittle over time, but it doesn't get hungry. There is nothing you can apply out of a can that reverses the aging process. Finishes do, however, protect wood from surface wear and grime. And they can slow (but not stop) the exchange of moisture.
Scott's Liquid Gold is an organic oil with no waxes or silicones. Oil finishes impart a warm glow to wood. In general, though, they don't offer as much protection as film-forming finishes like varnish or polyurethane. And they are not especially effective moisture barriers.
After years of foot traffic, to say nothing of frisky house pets, a floor's finish is bound to show signs of age. If you catch it soon enough, you can repair small areas without tackling the whole room--but it's very difficult to stain some areas and not others and end up with even color. It's probably going to look blotchy.
It may be time to think about hiring a professional floor finisher to sand down the floor and apply several coats of top-quality floor finish. You'll end up with a floor of uniform color and a brand new layer of protection. Although you can stain wood to just about any color you want, it would be hard to top the natural color of pine flooring from the 1870s. I'd leave that alone.
Get used to the cracks
As to the cracks that are showing up on some of the floor boards, consider them part of the character of your house. Unless there are obvious structural problems that are causing the floor to buckle, minor splits and cracks in the flooring are something you should expect. Enjoy them: they're part of the reason we like old houses.
A new condo probably has a near perfect floor. But none of the soul of your 1870s farm house.
An accomplished woodworker and carpenter, Scott Gibson is the former editor of Fine Woodworking magazine, and a former editor at Today's Homeowner and Fine Homebuilding magazines. He also is former managing editor of the Kennebec Journal, a daily newspaper in Maine.