Terracotta

[psd99]

Hi, does anyone know much about terracotta and the different types of pots available?

I walked into a garden centre today and I found a lot of italian terracotta and it was cheap like £9.99 for a 30cm pot

But it just felt a bit cheap and not really like the pots I already own
Which are far heavier. I did manage to find other pots which were like double the price but the quality far far superior.

The main questions around this issue is the fire rateness of these pots, are the heavier old school pots going to be more fire resilient?

I did wonder if anyone here has experience on this matter? I know it is a bit of a random one lol

 

[Cleisthenes]

I'm not sure on the actual hardiness, but there are definitely nicer pots than others!

I went here yesterday and they were stunning, 30cm pots are around 45 quid.

Pots & Pithoi · Earth refined

Quality Cretan terracotta pots and planters for the garden. Hand thrown using methods that have endured for thousands of years. Subtle variations in colour, texture and detail make each pot a unique a work of art.

potsandpithoi.com

 

[psd99]

They look like really good, solid quality

 

[martin363]

OK, technically terracotta is the 'least durable' of all clay types. Generally terracotta is cheap because the clay is largely unrefined, and the firing temperatures are low - 900 to 950c. Porosity is 7 to 15%, and they are not frost proof as a result.

The physical properties of terracotta are generally poor as a result of the above. Some 'terracotta's' are fired harder (higher temperature and made using better refined clays to reduce the porosity and provide a greater uniformity on clay particle size resulting in some of these pots being frost resistant, and marketed as such, but these are generally lighter orange in colour and heavier.

Fire resistance comes down to a number of factors, the key being thermal expansion coefficient. a pot containing a lot of air (high porosity) and less uniformity in particle size will not be as fire resistant as one improving on these parameters. Terracotta will not usually be especially fire resistant.

Your best garden posts are stoneware, the grey colour sand papery feeling ceramic (where it is unglazed). Good stoneware pots are fire at 1050 to 1100c, and will have a porosity of less than 2.5%. They are generally durable and glazed, considered frost proof etc.

Fire bricks are called fire bricks for a reason, no porosity, tiny particle size, high firing temperatures and low thermal expansion, plus usually contain a glassy phase to reduce or prevent crack propagation along the grain boundaries or between particles.

Hope that helps a little.

 

[psd99]

^^^^ Thanks and it does

in your experience why are some terracota pots far more expensive than others? for example a £30 pot, I can buy the same pot size for £8.99 but the £30 pot just feels much more stronger and durable

 

[psd99]

I am *Attempting* to make an indian tandoor oven you see... one of them projects that I was meaning to get around to and as the weather picks up perfect time to do this

 

[tom_e]

The physical properties of terracotta are generally poor as a result of the above. Some 'terracotta's' are fired harder (higher temperature and made using better refined clays to reduce the porosity and provide a greater uniformity on clay particle size resulting in some of these pots being frost resistant, and marketed as such, but these are generally lighter orange in colour and heavier.

in your experience why are some terracota pots far more expensive than others? for example a £30 pot, I can buy the same pot size for £8.99 but the £30 pot just feels much more stronger and durable

I'd guess that's why.

 

[martin363]

^^^^ Thanks and it does

in your experience why are some terracota pots far more expensive than others? for example a £30 pot, I can buy the same pot size for £8.99 but the £30 pot just feels much more stronger and durable

Price is generally driven by 5 things:

1. Quality of raw materials - 10 to 30% of cost.
2. Firing, temperature and time - 40%
3. Transport. where from, how and what size. obviously further and larger usually costs more. this used to be 10%, but has greatly increased recently. 40' container was $2000, now $12000, or thereabouts.
4. Margin, or number of margins in the chain
5. Also where they are made of course, cost of labour, and standards required in the factory, this can make a big difference.

If the pot is heavier (or stronger, denser) it obviously contains more material, and will require more energy to fire it, hence is likely more expensive to produce and of better quality.