Author Topic: Disintegrating terracotta pots.......  (Read 18232 times)

CotswoldLass

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Disintegrating terracotta pots.......
« on: February 03, 2006, 18:29:11 »
I know I bought most of them in a garden centre sale BUT all my terracotta pots on one patio are crumbling!

They are the typical 'bill and ben' shape, and it's the top ridge on all of them that had just disintegrated.

Very disheartening! Any ideas? Is it just the cold? (ones on the more sheltered kitchen patio are not so bad)

CLx

Curryandchips

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Re: Disintegrating terracotta pots.......
« Reply #1 on: February 03, 2006, 18:38:35 »
This sounds like frost damage, the terracotta absorbs moisture which then freezes when a frost occurs. The resultant ice expands which causes the terracotta to crack, and as you have witnessed, crumble. I have no idea whether this is due to the method of manufacture, but I have had the same happen to some of our pots. I think it is possibly the speed at which the freezing occurs which is the problem, slow freezing will allow the ice to form gently without cracking the terracotta. Your other pots are probably more sheltered, and thus do not freeze quite so readily.
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Gardenantics

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Re: Disintegrating terracotta pots.......
« Reply #2 on: February 03, 2006, 18:47:43 »
Yes it's frost damage! You can only trust pots that are fired to a high temp.  Only get the ones that say Frost Proof, as a guide try this little test (At the risk of looking a bit bonkers in the garden centre) Take a dry pot, and in a nice clean bit touch it with the tip of your tongue, if it grabs your tongue and won't let go, forget it! The higher the clay is fired the less moisture it will absorb, and when that freezes and expands the pot flakes apart. The only pots I trust are stamped Yorkshire Flowerpots in a ring around the pot. RHS shops sell them., cheaper in the long run, as they do last.

Brian

jennym

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Re: Disintegrating terracotta pots.......
« Reply #3 on: February 03, 2006, 19:15:07 »
Brilliant tip Brian. Just begs the question of how to answer the sales assistants when they ask why one is licking their plant pots...

CotswoldLass

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Re: Disintegrating terracotta pots.......
« Reply #4 on: February 03, 2006, 19:44:55 »
Very interesting, thanks for the input guys.

I'll wait a while before applying the 'tongue test' to prospective new pots - it is below freezing up here and can you imagine the scene in the garden centre if i were to go to the check out with my tongue attached to a terracotta pot!

Will check out the RHS pots for future......

CL x  ;)

grawrc

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Re: Disintegrating terracotta pots.......
« Reply #5 on: February 03, 2006, 20:12:56 »
Terracotta literally means "cooked earth". When exposed to severe frost, particularly if it's in a sunny spot it just disintegrates. Lots of places will tell you what degree of frost their pots will tolerate. But the licking test does sound much more fun. ;D ;D
« Last Edit: February 07, 2006, 18:51:12 by grawrc »

kitty

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Re: Disintegrating terracotta pots.......
« Reply #6 on: February 07, 2006, 18:31:19 »
speaking as a potter(well..an ex potter)the pots that'flake' are from foreign parts--they are 'bonfir fired-usually outside or in giant brick kilns.but,where preost proof pots should be fired to about 1000 degrees,bonfire heat usually only reaches 600 degrees...leaving the pots porous...
buy british-more expensive to start with but cheaper in the long run!
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CotswoldLass

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Re: Disintegrating terracotta pots.......
« Reply #7 on: February 07, 2006, 21:52:08 »
Thanks for that Kitty,

Had no idea, but from now on, will look out for British made pots, and be happy to do so,

Cheers,

CLx


Obelixx

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Re: Disintegrating terracotta pots.......
« Reply #8 on: February 14, 2006, 12:18:32 »
Meanwhile you can protect any remaining ordinary pots by painting them with a couple of coats of colourless acrylic varnish in matt or siatin, according to taste.  It helps also to lift the pots off the ground with those little feet you can buy so they don't stand in puddles and absorb less moisture.
Obxx - Vendée France

Gardenantics

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Re: Disintegrating terracotta pots.......
« Reply #9 on: February 14, 2006, 13:43:02 »
B&Q have good looking pots, BUT AVOID THEM THEY CRUMBLE! Also I noticed my local B&Q were selling off imported tin planters that are totally covered in rust, and they haven't even got off the shelves yet. I can't believe anyone would buy them even with 75% off.

Brian.

CotswoldLass

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Re: Disintegrating terracotta pots.......
« Reply #10 on: February 14, 2006, 15:52:18 »
No B&Q near us so I can avoid with ease! Thanks for the tip!

Obbelix, what about coloured varnish? I might just have some ideas.......

CLx

Obelixx

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Re: Disintegrating terracotta pots.......
« Reply #11 on: February 14, 2006, 16:05:25 »
Have fun CL.  I only said clear because I assumed you'd want to keep the terracotta colour.   The varnish won't last for ever but will help keep the pots looking good for longer and you caould always bring them into shelter for the winter if you do decorate them.
Obxx - Vendée France

tim

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Re: Disintegrating terracotta pots.......
« Reply #12 on: February 14, 2006, 16:12:17 »
"Frost Free"!

Skippy

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Re: Disintegrating terracotta pots.......
« Reply #13 on: February 14, 2006, 16:47:47 »
I am also a convert to Yorkshire Flower Pots!  They are excellent.  I've had them for 4 years outside in all weathers, and in North Yorkshire, where they have all survived intact.  They are also remakably cheap for what you get.  I am now in the process of asking for garden centre tokens for every occasion, and am going to gradually replace all mine.  You can also get them from one of the catalogues, maybe Harrods? (not sure) but they are more expensive that buying them from my local nursery.
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Gardenantics

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Re: Disintegrating terracotta pots.......
« Reply #14 on: February 14, 2006, 17:51:06 »
If you look closely the pots used in the Gardeners World Garden are the Yorkshire Flowerpots. For sale at Harlow Carr in Harrogate.
Buy it once, and use your old ones for crocks, I've not had one crack yet, and they are really heavy too, so very stable.

Brian

Vinlander

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Re: Disintegrating terracotta pots.......
« Reply #15 on: March 02, 2019, 13:12:09 »
Lots of pots marked as frost-resistant aren't, including many posh expensive ones with fancy patterns that were definitely made in the UK.

Losing these pots to frost is very expensive, so I never leave them damp or anywhere they can get damp during the winter.

There are 5 steps to bone-dry pots (which cannot be affected by frost).

1) Never put a perennial in a terracotta pot (unless it is something you are going to take inside - like citrus - but then avoid recurved ones like the plague - or you will never get plants out when they need bigger pots).
2) As a first action at least a week before your frosts can start, get them off anything wet - remove the drip tray and/or add "feet" to start the draining process.
3) When frosts are possible (before they are likely) either empty the pot or put it in a shed where it can dry fully with some protection.
4) The next step is to get the remaining pots out of rain: - by this time there should be more space in a largely unused shed, but you can also use tarps or inverted builders' bags or old tents in a sheltered area - if the pots can stay dry they are immune, but you have to accept the possibility of horizontal rain.
5) Don't use terracotta for any new plants outdoors before all risk of frost is past (and stick to annuals).

Incidentally, properly glazed pots tend to be a lot safer (unless you let them get very wet) - they are probably fired much harder BUT this doesn't seem to apply to white clay - especially smooth white clay with no obvious aggregate - pots designed to look like they are poking through a wall at 45o seem to use this and are the worst - totally hopeless, and so are any ornaments made the same way.

As for 'foreign' pots, the big thick-walled Thai ones made from a coarse mix look porous but are 100% immune (so far ~20 years) - but they are glazed - it just isn't obvious.

Flaking is terminal, but if they are in bits the easiest way to put them back together is to fit them together dry (no glue) so perfectly that the cracks are almost invisible and use brown tape to hold everything in place, then compress each crack in turn (tensioned tape can replace finger pressure) and apply superglue to the crack - it will sink right in and set (but not instantly - a few minutes).

When the whole pot is in one piece remove the tape and varnish that side. Then superglue the cracks from the other side - probably inside - and varnish that too. You can varnish the inside by putting a pool of varnish inside and moving it about by rolling the pot in your hands - a lot easier than getting a paintbrush inside - especially on recurved pots.

You can use any waterproof paint instead of varnish - even modern emulsions (a lot less smelly).

You end up with a pot that is a lot more immune than it ever was.

NB. if you find bits are missing then you can push polyfilla in the gap, smooth & mould & sand later - it will be invisible if you paint the pot (Majorel Blue is nice) but maybe you like piebald pots?

Cheers.
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Deb P

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Re: Disintegrating terracotta pots.......
« Reply #16 on: June 08, 2019, 10:24:45 »
That is a very comprehensive and helpful post! I recently purchased a job lot of old pots  and quite inadvertently followed your advice in repairing a few that had partial or complete breaks, good to know I did it correctly! They are all now in use, my rationale was if they have lasted this long they should carry on!
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