Removing oil-based stains from wood ceiling beams is not an easy task, unless you get to it right away. If the oil has been there long enough to soak in, it will take some more work to remove. The key is to eliminate the stain without rubbing off any of the finish. To that end, you should start with the safest methods and only precede to the riskier ones if necessary. For starters, you need to soak up as much of the oil as you can with a cloth.
Step 1 – Blot the Oil
When the oil is still fresh on the ceiling beams, get some paper towels and stand on a table, a chair, or a ladder. Stick the paper towel directly onto the affected area. Gravity will help the oil make its way into the towel. If you don't get to the stain in time, the oil will seep through the pores in the wood, forcing you to resort to stronger cleaning methods.
Step 2 – Use Mild Detergent
Mix some water and mild detergent. Soak a piece of cloth or sponge in the solution and squeeze out the excess water. Rub the affected area thoroughly until the oil is dissolved. To remove the detergent afterward, use a clean, dry cloth.
Step 3 – Use Vinegar
If the stain is a few hours or a few days old, create a mixture of 50% vinegar and 50% water. Pour this in a spray bottle. Spray the affected area with the solution and leave it for five minutes. Then, if the stain is gone, remove the solution with a dry cloth.
Alternatively, you can make a paste out of baking soda and vinegar. Rub this poultice onto the stained surface. Leave it for 10 minutes. Remove the residue by spraying the area with clean water and then wipe that off with a dry cloth.
Step 4 – Use Mineral Spirits
Mineral spirits are your last resort; use them only when the above methods fail. Wear some gloves, a mask, and safety goggles for this method. Dampen a piece of rag with the solvent and wipe the stained area clean. Keep going until the stain is no more and then remove the spirits with a cloth soaked in soapy water. Finally, wipe it dry with another cloth.