Varnish is used in woodworking to protect the final, finished piece of furniture or cabinetry. Varnishes are also used on wooden musical instruments to help them retain their gloss and sound. While you can purchase varnish at any hardware store, making your own at home allows you to adapt the recipe for whatever you are finishing.
Mix together one qt. boiled linseed oil, 1/2 pt. rosin or pine tar, 1/2 pt. Japan drier and one qt. turpentine in an old stockpot. Once you've mixed varnish in the pot, it should be reserved for this purpose only in the future.
Place the stockpot over medium heat. Stir constantly with a long wooden spoon until the mixture reaches a near boiling state. When you see little bubbles form on the outside edges, it is time to remove it from the stove.
Continue to stir the mixture until all ingredients are dissolved and the mixture has the consistency of pudding.
Allow the mixture to cool to room temperature. Add more turpentine if the varnish is too thick to brush on the wood surface.
Use the varnish immediately or store in an airtight glass or metal container until needed. You will need a one gallon container for storage as this recipe will make almost three qts. of varnish. Store the varnish in a cool, dry area. You may need to add more turpentine to the mixture if using stored varnish. Add the turpentine 1/4 cup at a time until the desired consistency is achieved.
Add more rosin or pine tar to make the varnish darker. Use less for a lighter colour. You can also use tung or walnut oil as a substitute for the boiled linseed oil. Overheating the varnish will cause it to harden into linoleum.