It is not necessary to use a paint sealer on clay pots. However, if you plan on using the clay pot to hold water or live plants, it will be necessary to seal the clay. Clay pots are porous and moisture will be absorbed into the clay. To eliminate this problem, use paint to seal the pot.
Patio paint is a type of waterproof sealant used on outside decking. You can use this same paint to seal the inside and outside of the clay pot. Anytime you plan on setting your clay pot outside or using the pot for live plants, this is the type of paint you can use to seal the pot. The patio paint adheres to the clay and prevents the pot from fading in the sunlight. If you want to brighten your clay pot, you can add a coating of patio paint clear coat.
You can use an acrylic paint to seal the clay pot if you plan on using the pot for decorative art. Ben Franklin Crafts recommends an Americana or Ceramcoat acrylic paint. The only time you can use this type of paint to seal the clay pot is if it will not be exposed to any water. You can use a spray sealer to cover the acrylic paint and brighten the colors.
Varnish is also a sealer you can use to paint a clay pot. It is best used with live plants. If you want to use and acrylic paint to color your pot and place live plants inside, use an exterior varnish on the inside and outside of the pot before adding the acrylic paint. This will seal the clay pot and prevent the clay from absorbing water.
A shellac is commonly used with unfired clay pots, especially if you plan on etching a design into the pot. The shellac seals the pot on the inside and the outside. The paint will brighten the pot and seal the pores of the clay. You will have to let the shellac dry for 24 hours before placing any plants or water inside the clay pot. Once it has dried, you will be able to see any places on the clay pot that you missed when applying the first coat. Add another coat and let is dry for another 24 hours.