Cleaning a butcher block with a natural-oil finish is fairly easy. First, use a soft bristled brush or a spatula to scrape away any food adhering to the surface of the block. Next, wash the board’s surface using a dish cloth dipped in soapy water. Once done cleaning the board, wash and rinse the dish cloth, wring it out, then wipe the block surface clean. Finish up by using a dry cloth to thoroughly dry the surface of the block. Be sure not to leave any water sitting on the wood surface, as this may cause water spotting. If any spotting does occur, you can renew the surface of your butcher block by sanding it and reapplying a generous coat of block oil or cream.
A butcher block with a Varnique finish cleans up just as easily. Use a dish cloth dipped in mild soap and warm water to clean the block's surface. Wash, rinse and wring the cloth, then use it to wipe the wood one more time. Use a dry cloth to dry the wood. Although Varnique is impervious to most household cleaners, it would not be wise to test its limits. And here's a final precaution: promptly clean up any liquid spills.
If you allow a board or block with a natural oil finish to get too dry, it could split or crack, so it's critically important that you clean and oil it regularly. This can also extend its natural beauty and useful life.
While the typical or average user should apply butcher block oil or board cream monthly, if you use yours heavily or frequently, you should oil it every two weeks to prevent it from drying out and cracking.
Also, exposure to extreme swings in humidity can swell and shrink a butcher block enough to cause checks in its surface, even with regular care and maintenance. To remedy this, apply a generous amount of oil and spread it evenly using a plastic grocery bag. (This is preferred to using a cloth, which will absorb and retain much of the oil). Smooth it out over the top and sides of the block and allow it to stand overnight. In the morning, remove any excess oil with a paper towel.
An especially effective maintenance regimen involves the use of both board cream and block oil. First, apply a coat of butcher block oil following the instructions above. The oil will penetrate deep into the wood maximizing moisturization. Then apply a board cream such as Boos Block Board Cream with beeswax to lock in the moisture and leave a silky, wax barrier on the surface of the wood.
If you notice minor cracks in your butcher block, you might try filling them with a cellulose filler in a tint that closely matches that of the wood. Allow the filler to dry, then lightly sand and re-oil the board.