Does Burying a Pot in Compost Create Patina?

When he was an apprentice here Andrew Robson puzzled over guidance we hear frequently: ‘Bury a new ceramic pot in compost and in a few months you’ll see patina on it’. Well, he took a new, unused pot and buried it in compost for fully two years. He watered it every day (true story). We just took it out, carefully washed it down, and here’s our results:

The difference is…drumroll…negligible. Or less. We actually could not identify any patina buildup whatsoever.

And here’s our pre- and post- photos of Andrew’s experiment:

Andrew took this pre-experiment photo of a new Roy Minarai pot, fresh from the kiln, before burying it in compost for exactly two years.

And this is after two years buried in nursery-bought compost. Granted, the lighting is a bit different making everything look yellower, but that’s deceptive. It’s just the bad lighting here with a warm bulb. The pot is also as shiny as the day it was made. In fact it’s eerily unchanged. There was a scant amount of residue on the inside, where the potter’s making marks held some of the dirt. But dirt is not patina, and there was no patina whatsoever visible on the glazed surface. Patina is the buildup of a residue that dulls the shininess of a pot, even changing the color of it to a more subtle hue, and is very desirable for making the pot look old. We didn’t see any of that. Although we can’t call this a myth on ‘one data point’, as Andrew says, we nevertheless remain unconvinced of the technique.

Just so we’re talking of the same thing…here are two images of VERY heavy patina buildup on old pots. These are over 100 years old. The actually glaze color of these is not a grayish cream, but the bright cream that is revealed in the scratch marks. So, we’re talking about residues that build up over a very long time, slowly, and they are quite durable (but can scratch! Hence in Japan, I was taught to be Very careful about repotting a tree in an old pot). Patina is not an acid that etches the surface (the glaze underneath is very shiny) and they are not lime buildups, which are white and are the result of hard water.

Scratches through the patina reveal the true glaze color, a light cream. The dark olive / gray over that is the patina buildup over decades. Most pots have nowhere near this amount of patina, but even a light buildup makes the pot dull, and infinitely more wabi-sabi. I’ve seen some lovely patina buildup in about 20 years; it’s a light wash but it’s there.

In this example the thick patina buildups have actually flaked off the bottom edge, causing it to reveal the light cream colored glaze underneath. These is NOT lime deposits, and though that is a common problem it is not generally referred to as patina.

Patina is a very valuable surface for a bonsai container, and yet in our first attempt to replicate it at a much faster speed, we utterly failed… But hope this clarifies what we were after in the first place. Pots with this surface are revered and highly valued and should be carefully handled.

13 Comments

  1. Judy Schmidt says:

    With the fires in CA and OR, everyone in the Midwest is concerned about the state of all of the bonsai schools and nurseries. Is there any place that we access information or provide contributions if necessary?
    BTW, I’m reading “Bonsai Heresy” and it’s enlightening.

  2. cenovak007 says:

    I heard you are supposed to bury them in the soil, presumably because shifting sand would wear at the finish. Perhaps you could speed things up by modifying the “Patina Buster”, as advertised in the Bonsai Wire podcast; or at least use a power washer with dirt mixed in? I’m sure Roy would replace the pot if it was accidentally destroyed.

  3. Chris Scott says:

    I’ve done that before to get rid of calcium build up and it worked great! Give it a try? I mean why not. Microbes gobbled up the free Ca and I got my pot back white crust free!

    Chris Scott Maine

    • crataegus says:

      Yes, it does work quite well to get rid of calcium build up. In trying to build patina though we’re trying for something else. I just uploaded a couple more images showing the sort of patina I’m talking about on old pots. Thanks for the comment-

  4. Ben B says:

    Perhaps a salt bath might be a quicker way to achieve patina

  5. Jon says:

    Hi,
    As a potter myself I hope to be able to add a small insight. The glaze will mostly be glass created from molten silica which is impervious to most things. A patina is, I think, created in one of two ways… 1) limescale build up through using ‘hard’ water which will give a slightly opaque patina that can be scratched off; or 2)an acid that etches the shine on the glass – this could occur if you were to use a very acidic soil probably high in organic matter (probably not great for growing the trees in!)
    So I would suggest burying again for another two years…. Look forward to hearing the results 🙂
    Best wishes
    Jon

  6. paul3636 says:

    Was it tried with an unglaxed pot????

  7. Dave Leppo says:

    The patinated pot images make me think that the effect might be duplicated by smoking the pots gently over a fire, like meat.

    • crataegus says:

      I see where you’re thinking. But carbon won’t stick to glaze, it rubs off easily. And seeing through the patina to the color underneath—whether a glaze or clay—is a major feature of it.

  8. Glen Mchargue says:

    I really enjoyed this article.
    It seems the only way to induce patina, and this is absurd, would be to create some sort of machine that cycles between a wash with a nutrient heavy water and then drying, then rinse (so the patina is more than just a nutrient build up) and wash and dry and rinse over and over. For a very long time. Essentially a bonsai life in fast forward. Which, I know, is silly.
    Maybe this is a good lesson that points back to why bonsai are so precious and captivating to begin with. They are a physical representation of an extended period of time. Thanks for the article!

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