Removing Glaze from Ceramic pots

Hello everyone!

I bought some Japanese ceramics and drilled some holes in it to turn them as bonsai pots.

I would like to unglazed the inside of the pot.

First if I would like to do it is because all the ceramic glazed pots are not glazed inside. I am wondering why exactly, and I guess it is for better breathability?!

I am also wondering how can I remove it in the inside ?
I found out you can sand paper it with a 220 grit.
I tried it but by hand it seems to be to hard if not impossible.
Is there any product to help removing the glaze ? Has anyone ever tried it ?
Let me know your suggestions on the process to do it and if it is worth it or useless.

Thank you for you help :pray:

Glazes are baked on at high temps. They will be very hard. I think you might be disappointed of the outcome of sanding glazing off.

A heavier grit sandpaper should be used to do the initial removal if desired. 40 grit maybe. Work your way to a smoother paper. 40-80-120-220. I can see this taking a few hours by hand. Some of the glaze will probably be imbedded in to the pours of the ceramic itself…YMMV.

Pots/Bowls/etc are usually not glazed in the inside because that part is not seen when a tree/plant/food is placed inside. Its a waste of time, energy and material for the potter.

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About the only thing that will dissolve the glaze is hydrofluoric acid which is extremely dangerous. In addition to being a strong acid it tends to attack calcium containing body parts (bones) without attacking skin and muscle. DO NOT USE IT!

I would not bother to remove the glaze. You will most likely have to keep the tree tied into the pot since the roots will not adhere to the inside of the pot, but it should be easier to remove the tree for repotting.

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I use a 80 grit sanding disk on a variable speed angle grinder to polish porcelain tile at work, a lower grit like 40 to 60 might at the very least cut the glazed surface. A diamond cutting wheel for tile will cut clean through tile, I use those to take rough edges off of tile. There’s plenty of options for grinding and polishing steel or paint. Maybe a steel wire wheel? Just some thoughts to get you thinking, a trip to the hardware store might get you going.

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How would the pot breathe “better” if there is still the glaze on the outside?

Ive used inside glazed pots for years. Because I like it as a bonsai pot. Carefully drilled hole; and notch the underside lip for drainage. Diamond drill and grinding tip s are easily available now.
Has never appeared to harm or slow down the tree.
I HAVE got comments on the QUALITY and good appearance of the pots and design. Experienced bonsai people are usually ok with them.

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Thank you all for your answers.

As good quality bonsai pots are very hard if not impossible to find here in Thailand I found out that there are a lot of imported Japanese or Chinese ceramics vessels. flFor a very cheap price sometimes. And it is a good way for me to make some cheap good looking pots, I am just concerned about not being able to notice a good and bad quality ceramic.
And it is a good way to find unique and original designs as all bonsai pots available here are generics low quality Chinese or Korean pots.

One of the differences between good and poor quality bonsai pots their ability to withstand freeze/thaw cycles. This is a result of both the clay and the firing temperature. Since most areas of Thailand do not freeze, you can probably focus on appearance.

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I heard like you can test with the sound they by hitting them gently with your fingers, I have 2 japanese cermaics that do a bell like sound, and one other unknown ceramic that doesn’t do any special sound, pretty like hitting a wood vessel.