What you'll need
Step 1 – Make Sure the Art Is Dry
Before you even begin mixing up your home brew of ceramic tile art sealer, you need to make sure that the art is completely dry. If you try to apply the sealer to paint that is not completely dry, it will run or be wiped off the tile. It takes longer for paint to dry on ceramic tile than on most common painting surfaces, so take that into consideration. You also need to consider the humidity of the area you are working in. High levels of moisture will cause the paint not to set. Whatever the drying time is for the paint you are using, always double and even triple it to be certain it is set.
Step 2 – Using Alcohol
Alcohol is fast drying and can be used to set the paint on the ceramic tile just prior to applying the sealer. Alcohol can, however, damage paint, so it is important to test the alcohol on a very small area of the paint. Use a cotton swab to do this. If the paint dissolves, then use the alcohol very carefully. Otherwise, you can paint it on the tile as you would any other paint or sealer. Some kinds of paint can come off when you scrub it with alcohol. Prevent this by soaking a rag in alcohol and draping it over the tile. After several seconds, you can carefully remove the rag. The alcohol will dry in seconds and, in the process, will set and protect the paint.
Step 3 – Linseed oil
This type of oil is very safe on most paint products and also safe to use on glazed ceramic tile. Once the alcohol has dried, paint it on the tile over the art. Use a clean rag to dab up the oil but never scrub or wipe it off.
Step 4 – Make a Sealer
If this is a hobby you do often, then mixing your own sealer will prove beneficial. In a mixing bowl, pour in four parts of linseed oil. Thin the oil out with one part alcohol.
Source: www.DoItYourself.com