Can pots made from wood ash be used to grow plants ?

Hello there, if you know the Youtuber Primitive Technology, he recently made a video where he us wood wash to make a solid pot.



I'm wondering, could pots made this way be used for gardening ? AFAIK, you can make cement with technique like these (some guys had done so in a video, and made a pond with it), but the issue is that the water held within would become alkaline, and become toxic to the fishes living in it. However I'm no expert, and my source is a youtube comment, so obviously it's not from a certified expert. Would the same problem happen with plants, and if so, how can you mitigate it ?

Thanks !

A. Did anyone else cringe at the sight of him handling wet ashes with his bare hands? I've known people who lost all the skin off their hands that way.

B. At one point it looks like he's mixing something else in with the ashes. Something that's almost the same color, but with a slight beige tinge. Was that clay maybe? Because that would make a lot more sense. Ash and clay would react to form something akin to concrete. I think there's another thread about that here somewhere.

C. It looks like the pond he soaked the items in is slightly acidic. That probably did a lot to neutralize any unreacted ash. You could probably get a similar effect soaking it in very diluted vinegar or black tea. I have no idea what soaking his items did to the pond life.

Wood ash has a lot of alkalinity (they make lye soap with the leachate from hardwood ashes), that means you pH of a container made with it will be far above the neutral level of 7.0pH probably more like 12.0+ pH would be likely.
Using wood ash for making concrete for a pond might sound like a good thing to do but I'd want to do lots of testing not only of the method but of the pH of the final product before I made the decision to attempt this one.

Redhawk

Ellendra Nauriel wrote:A. Did anyone else cringe at the sight of him handling wet ashes with his bare hands? I've known people who lost all the skin off their hands that way.

B. At one point it looks like he's mixing something else in with the ashes. Something that's almost the same color, but with a slight beige tinge. Was that clay maybe? Because that would make a lot more sense. Ash and clay would react to form something akin to concrete. I think there's another thread about that here somewhere.

C. It looks like the pond he soaked the items in is slightly acidic. That probably did a lot to neutralize any unreacted ash. You could probably get a similar effect soaking it in very diluted vinegar or black tea. I have no idea what soaking his items did to the pond life.

He usually has a full explanation in the description of the video but I don't see mention of what he added this time.  On his website there's an entry for making cement with ash and he added crushed terracotta, I suspect it's the same here.

https://primitivetechnology.wordpress.com/2018/07/17/wood-ash-cement/

This topic has been bugging me, so I did some more investigation. Starting with the chemical composition of wood ash.

It turns out, roughly 50% of wood ash is calcium carbonate. The same stuff that's in limestone, shells, and bone. Washing the ashes brings that percentage up, by getting rid of some of the more water-soluble compounds. After washing, it can be treated the same way you would other forms of CaCO3. Yes, it would still have some impurities, but so do the shells, stone, and bone.

I knew there was some calcium in wood ash, but I had no idea it was that much. This opens up a whole new source for home-made concrete.

I would guess that the washed ashes could also be neutralized with a small amount of vinegar, and used to improve the calcium content of garden soil.

My property doesn't have a whole lot of wood, but I might take some ashes from foxtail grass and get it analyzed, to see if the composition is similar enough. I have foxtail like you wouldn't believe.

My general impression of this video was hmm, ash supply. I suspect that clay pots are a far more abundant resource than ash pots. So I would make both types of pots. If the ash pot didn't work for growing plants in, I would only make ash pots for other uses and use the clay pots for growing plants. If I didn't have clay (deep sandy soil perhaps), I would probably just do without pots for the most part.

Just brainstorming potential sustainable pots / containers for plants:

Soil Blocks

Paper Pots

Baskets

Clay fired Pots

unfired clay?

Wood pots and or wood flats

Ash pots (suitable?)

Concrete pots

Soil on top thick layer of leaves/grass/bark/sawdust

Some kind of natural resin such as pine sap might be somewhat equivalent to plastic pots

cow pots- might be possible to make a homemade version, particularly with the fresh stuff.

I suppose what we grew plants in would and will be constrained by local resources. Of course there is also the option of growing them in the ground, which cuts out a lot of pot making.

The Jeavons "How to Grow More Vegetables" system uses wooden flats. Sustainable? Maybe. Can we just direct seed our plants into the ground and cut out this step entirely? Maybe, at least in some cases.

So I guess the answer then becomes, cut out pots wherever possible, then use whatever sustainable resource is most abundant and or best bang for the buck in terms of optimizing its ability to last vs. its abundance locally to grow what has to be grown in pots. Maybe that's ash pots for some people.

Wonder how hard it is to make glass? Say you have lots of sand and no clay. You need a pot like container. Can you melt the sand to make glass?

https://www.youtube.com/watch?v=BEiat9O74ms