Just checking,
I saw a glazed pot at Target and on the bottom there was a sticker that said that pot was not for food use or something like that. Does that mean I shouldn't grow vegetable plants in it? And if so why? And...does this apply to all glazed pots? I'm asking because I'd like to grow kitty grass for my cats in a glazed pot I already have (not the one I saw at Target with the sticker on the bottom.
Stupid question over,
Layne
ps, thanks!
It probably means the glaze contains lead, or they don't know if the glaze contains lead. Lead is not particularly mobile in soil, I would not worry about it; I might mix some crushed limestone with the potting soil to make sure the pH is not too low, but it's not like you were drinking orange juice or lemonade stored in the pot.
Best regards, Bob
Some pots have low fired glazes comprised of toxic compounds which could leach into food products. They are not intended for food for human consumption to be served in. There is no problem with using these for growing cat grass, although I might not consider them very good for other vegetable crops you intend to eat. For one thing, they tend not to be very durable and will not weather well outside. They also tend to be cache pots with no drainage holes - a decorative item you put another pot into - so they look like they could be used as a serving piece. Pots and ceramic containers designed for growing plants out of doors generally are high fired and have no similar concerns.
The porous clay pots are better choices for plants because they allow more air to the roots. Glazed pots would be a good choice for bog plants. Some glazes contain toxic or even radioactive (!) compounds.
Even more interesting is that many of the pots for sale these days come from China, where anything goes as far as environmental safety. The rap goes something like "Economic growth trumps minor issues like safety".
Thanks for the responses. :-)
Layne
Definately heavy metals in the glazing. Lead or Cadmium which over time the human body seems to collect and store.
I'm curious. Do *all* glazed pots have harmful substances in the glaze? I mean we eat and drink from glazed cups and bowls?... Is there any way of knowing if a glazed pot contains harmful substances?
Layne
The use of glazes is regulated. In general dont trust in cups or bowls with bright colours as reds or yellows. Particualrly if the bowl or cup is made as decor object. You can put lemon juice in them, if the glaze loose the finish, then could be possible be toxic
Crayons are regulated too, but that didn't stop the Chinese from using lead pigment in crayons and selling them to the US with fake "ASTM" safety markings on the box. That was about the same time we made them "most favored nation" trading partners...
Best regards, Bob
Commercial glazed ceramic ware for table use is fired at high enough temperature to burn out the lead and other metals. There are lead test kits available if you are worried that your dinnerware or flowerpots might be contaminated.
About 50 years ago Fiesta Ware produced a red glazed ware that was made with uranium salts in the glaze. It was radioactive, but it was not really dangerous as long as you didn't use it frequently with strongly acid foods.
Pieces of it are valuable items now.
J. Del Col
Dont you have testing labs for imported goods ?
The iffier the origin of the glazed ware, the iffier the glaze itself. Anything from Mexico should be automatically suspect (traditional glazes there leach much lead, and Mexican potters have been very reluctant to change); commercial ware made in the US, Japan, or northern Europe (particularly the UK) should be OK; everything else is somewhere in between.
This is not at all true. Lead is volatile and not used in high fire glazes, but it is used in low fire glazes and other metals such as copper, cadmium, and cobalt are used in high fire glazes. These metals, even lead, can be safely used if the glaze is properly formulated and fired, but unfortunately this is often not the case.
deg
Thanks for all the additional info. I found test kits online and will buy one to test this pot and the bathtub glaze.
Thanks,
Layne
Last time I was in an Ace Hardware store they had packages of swabs that test surfaces for lead.
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