Q's on concrete pots (leaching/pH, sealing the inside, ect)

[SU2]

I've just made the first of many containers/slabs for my trees and, after ~1wk in its form, I took out a 10" circular pot, sanded it and now have it in a bucket of water to get pH down from the highly-alkaline cement (I did 1:2.5 cement:sand)

While I know that a month of leaching it in water will dramatically reduce the pH, it's still not inert at that point (pH of >9 at 1mo!) and my specimen like <7pH so this matters to me! I'm now thinking about options for sealing the inside of the pot, to form a barrier between my substrate and the container, and am hoping for thoughts on this approach as well as specific recommendations on what could/should be used! I'm unsure if I want to paint the exterior or just leave it raw, but understand that, if I sealed the inside, I'd have to wait a while before doing any outside seals (though presumably I could use sink-in stains/pigmentation if I chose, just not a hard/glossy paint finish, at least not for a while)

Thanks for any tips on this, am just getting-going here but very excited for some great containers & slabs, hopefully will get to my 2nd one (a slab) today!!

 

[Quince]

I have a few concrete pots, but I never bothered to seal them, honestly I worry more about cracking in the winter and water pooling in the imperfect bottom. One of them is home to a Savin juniper, and I haven't noticed any obvious pH problems.
Polyurithane or epoxy might work as barrier, but i would expect the epoxy to hold up better.

 

[clevetromba]

I have a few concrete pots, but I never bothered to seal them, honestly I worry more about cracking in the winter and water pooling in the imperfect bottom. One of them is home to a Savin juniper, and I haven't noticed any obvious pH problems.
Polyurithane or epoxy might work as barrier, but i would expect the epoxy to hold up better.

I second that advice. Polyurethane is generally not formulated for damp conditions, epoxy is. On the other hand, if you wanted to paint the exterior, the reverse is true: epoxy degrades quickly with UV exposure, while polyurethanes are more resistant to UV degradation.

 

[Josh Barg]

Polyurethane will peel off of the cement. You can use a cement impregnator. It doesn't really change the appearance or feel of the cement but creates a barrier from water, almost like rain x on your windshield it just beads off of it. You can find it at Home Depot or most building supply stores.

 

[Anthony]

We soak for 6 weeks, when the mosquitoes can breed you are clear.

J.B.Pines in the concrete containers have no problems.
For acid soil types, try a little Peat moss.

As a coating on the outside, Petroleum wax and mineral spirits.
On the outside however and can be coloured like a glaze coat.
Thin coat okay.

As usual test with cuttings all new plants in pots.
Good Day
Anthony

 

[sorce]

https://www.bonsainut.com/threads/those-pot-materials.18202/

Sealer and Concrete #'s should be in page One.

Move to clay ASAP!
I was up till 2 last night!

No Freeze for personal use...
Low fire ease.

Sorce

 

[SU2]

Polyurethane will peel off of the cement. You can use a cement impregnator. It doesn't really change the appearance or feel of the cement but creates a barrier from water, almost like rain x on your windshield it just beads off of it. You can find it at Home Depot or most building supply stores.

I wonder if it's inert so far as biological stuff, like if it's OK for the roots once cured? Imagine I'd just have to try and see!

We soak for 6 weeks, when the mosquitoes can breed you are clear.

J.B.Pines in the concrete containers have no problems.
For acid soil types, try a little Peat moss.

As a coating on the outside, Petroleum wax and mineral spirits.
On the outside however and can be coloured like a glaze coat.
Thin coat okay.

As usual test with cuttings all new plants in pots.
Good Day
Anthony

I like the idea of 'when mosquitoes can breed' as a metric

Are concrete containers stronger than comparably-sized ceramic pots?

Am confused how you phrase the coatings, do you mean petroleum wax/mineral spirits on the inside?

And lastly, I see that reco a lot, to use peat moss (the decomposed sphagnum, right?) for acidity - wouldn't that negate the point of using large-granule substrates? Peat moss is so fine I'd be worried of ruining my airy mediums, would sulfurs be just as good an approach?

 

[SU2]

https://www.bonsainut.com/threads/those-pot-materials.18202/

Sealer and Concrete #'s should be in page One.

Move to clay ASAP!
I was up till 2 last night!

No Freeze for personal use...
Low fire ease.

Sorce

Why do you say 'move to clay asap'? Oddly enough I just wandered-into a ceramic store, they sell stuff but also do classes, seems they try to steer you to doing projects (as opposed to just selling stuff), I'd asked the woman about planters and we were chatting and she seemed to think cement-based would be stronger than ceramic-based when both are same dimensions, would love your thoughts on this! We don't get freezing temps here (well, rarely!) so am not as worried on that!
(also confused what you mean by 'low fire ease.'? I'd looked into DIY ceramics but cement seemed so much easier so I just went that route, though I'm always amenable to change!!)

Great idea on those baskets, would like bottom drainage but the colander / air-pruning effect is what's most important so good job! I like them but would sooner make pretty containers and just buy colanders (have about as many extra colanders on-hand as I do 'traditional' containers, love love the idea of air-pruning and constantly think of ways to incorporate it, have an idea for a box that's got slits in the sides with metal-mesh to retain substrate, will see if I get to those as the cement containers are now my aim!)

Thanks for sharing that link

 

[Quince]

Concrete is strong under compression but not so strong under tension. That's why concrete is usually reinforced with steel. My guess is that good stoneware is both stronger and less porous than concrete. I chose concrete as a material because it's easy to use, and I don't have a kiln.

 

[barrosinc]

I like the idea of 'when mosquitoes can breed' as a metric

it's better than imperial measurement

 

[sorce]

Why do you say 'move to clay asap'?

Or that mold crete,@soldano uses..
There's a thread somewhere.

Clay is more satisfying.

Low fire tropical pots can be made with less $ .

Sorce

 

[SU2]

Or that mold crete,@soldano uses..
There's a thread somewhere.

Clay is more satisfying.

Low fire tropical pots can be made with less $ .

Sorce

Your writing always confuses me, am unsure if your english as 2nd-language or your writing style just doesn't jive with my ears lol Can you elaborate on the 'low fire tropical pots' costing less? Because price matters to me, I'm as DIY as possible to be able to be in this hobby, I'd spent ~$6 on a 50lbs bag of pure cement (that I mix 1:2.5 with sand) so can make a ton of containers out of that, I'm definitely interested in other approaches if they're viable though!!

 

[sorce]

Your writing always confuses me, am unsure if your english as 2nd-language or your writing style just doesn't jive with my ears lol Can you elaborate on the 'low fire tropical pots' costing less? Because price matters to me, I'm as DIY as possible to be able to be in this hobby, I'd spent ~$6 on a 50lbs bag of pure cement (that I mix 1:2.5 with sand) so can make a ton of containers out of that, I'm definitely interested in other approaches if they're viable though!!

High fire is frost proof.

The higher the fire the more the energy the higher the cost.

You can get away with ancient techniques that cost only time.

Sorce

 

[SU2]

High fire is frost proof.

The higher the fire the more the energy the higher the cost.

You can get away with ancient techniques that cost only time.

Sorce

You nonsense rascal, you speak in riddles lol! What are these ancient techniques you speak of, what terms would I google to get me there? Am quite interested in doing ceramic alongside my cement pots, it just seemed that having to buy/build a kiln and all that made it prohibitively expensive when compared to cement..

 

[sorce]

Something like that....

Sorce

 

[SU2]

Something like that....

Sorce

Thank you very much