A butcher block countertop can be the focal point of your kitchen whether new or a remodel. This type of counter top can last for years if sealed properly. There are some safety issues to keep in mind when sealing your butcher block counter top.
The best sealent for your butcher block counter top is either mineral oil or walnut oil. These are the two most widely used sealents and are safe to be around food. Mineral oil will retain most of the original color of the wood darkening it only slightly. Walnut oil will give it a darker color. They are both applied the same way. Wipe your butcher block with a soft cloth to remove crumbs or dust. Pour a puddle of the oil onto the counter top and work it into the wood with a clean, soft cloth. Make a motion like you are pushing the oil into the wood. You should wear rubber gloves to do this. Let the oil sit for about 20 minutes to soak in, then wipe lightly with a clean cloth. You can use your counter top in about 12 hours.
Do not use linseed oil, which is not safe around food. Other stains and varnishes will have information on the container if they are safe around food but most commercial stains and varnishes are not food safe. The Federal government has guidelines for sealants that come in contact with food and have published a guideline. Also, any solvent that comes in contact with food must have a MSDS (Material Safety Data Sheet) available for the consumer with all information about the product.