Post 64 Some pots from my collection

Another Christmas has come and gone and this will be the first for many years that I didn't score a new bonsai pot for a present. For a long time that has been my standard request for and ABC event ( aniversary, birthday, Christmas). At least I can't be accused of being boring anymore- well at least not for that reason.

The motivation for getting into making my own pots was about getting bigger and better for less. I didn't know a lot about pots before making them myself and I think many enthusiasts would be the same.

Most people at some point in their lives will have bought ceramic tiles, for a reno job, a new house or simply repairs. If you reflect on that purchase you might recall the information available about the different types and classes of tiles for different applications and what they may be exposed to.
 There is a clear distinction between non-vitreous, semi vitreous and vitreous tiles. This classifcation has much to do with the type of clay and the firing cycle it may have been matured to. You would chose between them depending on whether they were to be located inside or out, on the floor or the wall etc. There is a clear quality, service capability and price relationship at work with ceramic tiles and you get what you pay for.

Such a pity then that the same level of information is generally not available when purchasing bonsai pots, beacuse the same considerations should apply; what sort of clay was a pot made of, how was it fired and how will it perform in service.

This pot for example is a nice shaped little unglazed oval pot about 370mm long. Before taking the picture I gave it a vigorous wipe down with a damp cloth and then let it dry, no brushing. The pot has been out in the weather for years. It has provided good service but before even thinking about using it for a displayed tree some serious work would be needed. Actually now I wouldn't even think about it. It's just a grow pot and I'm just keeping it long enough until I have one of my own to take its place..

As you see there is a whitish deposit on the surface of the pot. This might be lime scale but I have others of a different origin which do not suffer from that so I am more inclined  to think it is efflorescence, the migration of slightly soluble salts from within the ceramic material to the surface; the sort of thing often seen on new brickwork. This is a reflection on the quality of the original clay body and what may have been added to it for various reasons. I suspect this is a low fired earthenware ceramic material which in tile terms is non or semi vitrified, which gives it a level of porosity that allows water to move through the pot wall and carry salts to the surface. That porosity also allows and supports unattractive biological patina to grow on the pot, futher diffusing the appearance and colour. Unfortunately in the absence of information about where it came from, how it was made and its qualities you don't know if the pots you buy will look like this one in a few years time.

I now know you can tell a low fired pot from a high fired pot by the bell test. Support the pot on a finger through a drainage hole and wrap the pot with a knuckle - to get anywhere from a thunk, to a ping to a resonant bell.  If you don't want a pot that looks like this one then if they don't ring like a bell don't buy them. A drop of moisture on the pot wall will also help you understand its porosity, a key influence on future appearance.
Knowing what I know now and having made and used pots in both earthenware and stoneware, I would never ever buy an earthenware pot again. If it wasn't stoneware I wouldn't touch it no matter what, I'd rather use a plastic pot.

Glazed pots are a different challenge to assess.
 

 This pot is a shohin sized glazed oval. It also is a few years old and has spent all that time out in the weather. When I bought it the glaze was a most attractive high gloss and you can see where it has run in the firing to give a gradation in colour under the rim. The picture is a truthful illustration of its current state. The glaze now looks like it's been sandblasted to remove the gloss leaving a very dull surface appearance. Once I just thought that a glazed ceramic surface was glasslike and forever. Now I understand the chemistry and that is only so under certain circumstances.

Most folks will at some time in their lives have been in a limestone cave - stalactites and stalagmites etc. They take a long time to get like that and have come about through dissolved limestone redepositing from drops of calcuim carbonite rich water evaporating and leaving the crystaline material behind. That's why the mites and tites sparkle. But of course how did the limestone dissolve in the first place. Well easy really; as rain falls carbon dioxide in the atmosphere dissolves in the rain, turing it into dilute soda water, otherwise known as carbonic acid. Dilute acid will also attack the surface of a glaze, if it is not correctly balanced and stable. Glazes which are used on ceramics for food service by professional suppliers will be formulated to be resistant to attack by dilute acidic food materials; it is possible and simple enough.

So back to the pot. The little blue / green pot glaze is what I call a showroom glaze; looks great in the showroom, but never ever take it out in the weather or it will wash off! Yes it really does start to wash off over time and it's the surface, the reason you bought the pot,  that goes first. I've got a few pots like this, how about you? This is a really difficult issues to deal with at purchase time. The only way to beat it is to know where your pot comes from and how it has been made.

If you are interested in how your unglazed and glazed pots will look after a few years out in the weather and your retail pot supplier offers no information about their pots other than price, then pretend you are buying ceramic tiles and ask more questions. This is why I now make my own but there was a time when I decided to go right up market; next time I'll show you my two Tokonome pots.