Terracotta pots. Frost proofing?

I have had some terracotta pots for a few years now, which are supposed to be frost proof, however, one has started to break and peel in spots traditionally conducive of frost attack.
Is there anything one can 'paint' onto them to make them less effected by said frost?

 

Unfortunatley Fonzie, the problem lies with original firing of the pots in the kiln. The lower the temperature they're fired at, i.e., under 1000 degrees C, the more suseptible to frost damage they are. Sadly, most imported teracotta is fairly soft, that's why it's cheap.
Whichford pottery make some fabulous pots but unfortunately at fabulous prices. Luckily, I have a local pottery, www.aylesfordpottery.co.uk , who have just made some BIG pots for a client at a much better price, and they're guaranteed for 10 years.
As to what you can paint on, I'm not aware of anything that will preserve them, as the problem is water getting in to the under-fired clay. Mind you, I expect a lot of "frost-proof" pots, will have suffered this winter. Sorry not to have been more help.:(

 

Fonzie, terracotta pots are NEVER frost proof. The better ones are frost RESISTANT, but not frost proof.

 

Fonzie - I don't profess to have any particular knowledge of terracotta pots, but a bit of science tells me that there are two ways in which frost can damage a pot.

The first is when the entire pot splits in two. This is caused by the soil in the pot getting waterlogged, then freezing. When water freezes it expands and it can burst the pot in the same way that it can burst water pipes in the house. The force of expanding ice is so great that it will crush ships hulls in the artic, so there is no such thing as an unbreakable pot. However the thicker and stronger the pot is the harder it will be to break. But there is a solution to this, and that is to stop it getting water logged. You can do this by improving the drainage of the soil in the pot with added sharp sand and grit. I have a large pot that it too heavy to lift, and over winter I remove the plants (which are tender) and cover it with a black bin liner, which just fits. If water can't get into the pot, it can't expand when it freezes and the pot can't split. You could also put the pots under cover or just under the eaves of the house, where they will be much drier. An empty pot can never split this way.

The second way that frost can do damage is when water soaks into the porous terracotta itself and then freezes and expands. This won't split the entire pot, but flakes will come off. And the more that flakes come off the more porous interior they expose, and the worse it will get in time. The solution to this is to stop water getting into the interior of the terracotta, by givng it a waterproof coat. Glazed pots have this waterproof coat in the glaze, so are more resistant. But no glaze is totally perfect and once moisture gets in it will chip and become worse. I don't know the best type of coating, but if you apply the principle, you could use household gloss paint if you want colour or something like marine varnish if you don't. The key is to get a waterproof coating.

 

Lost quite a few pots this winter glazed and unglazed some empty and upside down to prevent damage but they secumbed.:(

 

Sorry to hear about that Walnut - they can be rather expensive to replace. I can only think that water must have got inside the terracotta itself and then frozen. I can't see that cold by itself can harm a dry pot. I have been lucky so far, but once they start to go the damaged area lets more water in and can quickly damage it more.

 

Me too Walnut ... some of the nice embossed design has split away :( and our patio is paved with glazed tiles and lots of them have lost patches of glaze. personally I can't stand them, and they are slippery as an eel when wet [thus dangerous], but I hadn't been in the mood for affording to replace them any time soon :(