The evaporation although more than in plastic will help to cool the roots more than plastic. If you have a good drip system and a cheap supply of pots and it sounds like you have both I personally would leave it alone and use to your hearts content all the terra cotta you want. I am planning on using a plastic black pot in a terra cotta (big) so I can repot more readily when the palm tree needs it(which it does this spring). That is the biggest down side IMHO of terra cotta. That and weight and expense. But repotabilty (is that even a word:) is most important to me. You need to decide what the most important factors are for you and go for it. I wish I had your choices and I know my wife would prefer I used more decorative styles of pots but ..... the above factors are how I choose to container grow at this time. If you decide to seal there was a tar like material I used several years ago at a Home Depot that brushed on and dried well and kept my wifes artwork on the outside in good shape for several years. Hope this helps you decide what is best for you. Happy Growing David

Bonding primer. Like Sherwin William's PrepRite Bonding Primer. Here is a link that might be useful: More PrepRite Info

Oh GOOD! I can finally contribute to something I KNOW about..I LEARN sooo much here, and see beautiful crafts, now and then I pipe up and say a thing or two, BUT THIS IS MY THING!!! :) I seal after I paint, Patio Paint has already got sealer in it too, and they make a clear coat sealer. I paint my pots COMPLETE, that could be because I'm a little "anal" though!:) I have done a lot of differebt versions where I only paint the rims and bottoms, or only the top inside rim along with the entire pot. LET ME TELL YOU....THE BEST deal I found was at Wal-Mart about three weeks ago on terra cotta pots, they were practically FREE! The most I paid for one was $1.25, and that was the BIG 16 inch pot. The standard sizes were a dollar or less, I STOCKED UP because I paint the pots and sell them. The most expensive place I have found for pots is JoAnn Fabrics, and Michael's...any craft store of course will cost more. The pots are on clearence now though at Wal-Mart, you should go check it out!! You will SAVE money no matter what!!! The pots soak up the paint so well, I have found that the ones made in Germany give the smoothest finish too...it may sound strange, but I have done A LOT and have learned which pots are better. Let's see, I reccommend the Patio Paint brand completely, it isn't thick, it's easy to work with and it's inexpensive too. Wal-Mart sells bottles for .99 each. You can pay up to $2.00 a bottle at craft stores for the same brand. HAVE FUN!! Good luck and I certainly enjoyed sharing!! Thanks!!

Maybe the problem is the paint or the clearcoat you put on first. The Thompsons isn't going on terra cotta, it's going on what you put on the terra cotta.