[DIY mortar pots] Sealing the inside of pots to prevent pH affects?

[SU2]

I've got my 1st container/pot sitting in a bucket of water that I've changed ~daily for 3wks now, so in a week it's 'ready to use' or at least as close as it'll ever get...

Cement has a pH that's pretty alkaline (not the stuff that's being leeched-out, but actual cement, like 10y/o planters would still have an alkaline pH), and most of my trees are bougainvilleas which prefer acidic - I've gotta say that even if I waited another 3wks before taking that planter out of the leeching-bucket and use it, I'd still be very worried, there's so much container//substrate interface and, being constantly wet, I'm betting the substrate's pH will be affected (I should probably get a pH kit to gauge this, but even w/o that I know it will have an alkaline effect)

So, is there a practical/safe sealant? I don't know the first thing about ceramics or their glazes, and I know I'd be incredibly hesitant to use the clears I know about (polyurethanes) - am hoping for recommendations on what could be used to coat the inside of my container, not only for pH but to prevent the roots from just biting-into the container (making re-potting a bad thing for the roots), and the best idea I have that I know is safe is to just use vegetable oil, am hoping someone can suggest something a bit more elegant!

Thanks for any advice on this, I've only made 1 pot so far but I bought a 50lbs bag of cement (made my pot with 2.5:1 sand:cement) and am planning to really get going making a lot of containers (pots & slabs), the only thing is that I'm hesitant to go all-in on this knowing cement is alkaline and my bougies like acidic :/

[attaching pic of container, 50% for context, 50% because I haven't been able to show anyone irl ;P ]

 

[sorce]

Didn't I link you that quick crete cure and seal?

Ready for use next day!

Nice shape!

Sorce

 

[M. Frary]

I'd still be very worried

Then why use it?

prevent the roots from just biting-into the container (making re-potting a bad thing for the roots

You will be cutting them back at repot time any way.

 

[jeanluc83]

One of the hobbies that I almost got into was saltwater reef aquariums. I quickly found out it was much too rich for my blood.

It is common to make your own cement "live" rock. There was a lot of discussion on getting the pH to be neutral. The common method was to do just what you are doing and put them in a bucket of water that gets changed daily until the pH is neutral.

Another that would work for small pots is to put them in your toilet tank. The water is cycled many times a day so the pH should stabilize fairly quickly.

One other is to find a local stream or lake and put it there for a few months.

Personally I would think that soaking for a few weeks would be sufficient. Unless your trees are very pH sensitive I don't think it would make too much of a difference.

 

[GrimLore]

I have that I know is safe is to just use vegetable oil

Don't use that, use Mineral Oil far safer for a variety of reasons. Myself that is all I would do, after a few good soakings in water I cannot see PH being an issue.

Grimmy

 

[SU2]

Didn't I link you that quick crete cure and seal?

Ready for use next day!

Nice shape!

Sorce

I must have missed it (or am just going out of my mind, equally as likely at the moment tbh, too busy, will be quite embarrassed if it's the exact product I need and I missed your post

Then why use it?

Because I want to be able to craft a lot of pots and ceramics didn't seem the better path, I'm partial to cement/masonry so concrete containers/slabs have a huge appeal to me, something as trivial as figuring out how to properly seal the inside certainly wouldn't dissuade me!

You will be cutting them back at repot time any way.

For sure, but when removing a pot-bound tree (it's good to let bougies get kinda pot-bound before re-potting) the roots on the side can easily be severed with a blade, but there's far more surface-area along the bottom-face of the pot, and the roots will be biting-into the nooks&crannies that make up the 'flat' bottom of the pot.. I know it's not going to be devastating to the tree to break some extra roots but I'd sooner the inside were sealed/glazed, it makes the roots unable to bite + eliminates pH concerns + helps retain moisture in an otherwise-porous/wicking material, sealing the inside just makes sense whether I finish the outside or not!

One of the hobbies that I almost got into was saltwater reef aquariums. I quickly found out it was much too rich for my blood.

It is common to make your own cement "live" rock. There was a lot of discussion on getting the pH to be neutral. The common method was to do just what you are doing and put them in a bucket of water that gets changed daily until the pH is neutral.

Another that would work for small pots is to put them in your toilet tank. The water is cycled many times a day so the pH should stabilize fairly quickly.

One other is to find a local stream or lake and put it there for a few months.

Personally I would think that soaking for a few weeks would be sufficient. Unless your trees are very pH sensitive I don't think it would make too much of a difference.

Yeah it's a money-pit for sure, however Craigslist is a gold-mine for marine equipment (and gym equipment!). Re "changed daily til the pH is neutral", that wasn't my experience- even after a looong time soaking, the pieces of 'rock' would still raise the pH of a fresh bucket of 7ish pH water, I'm gonna get some pH strips so I can test whether an aged (like ~1yr+) piece of cement in water will raise its pH, am suspecting it will I just don't know how much..

Your stream/lake idea is so fucking awesome, thanks a ton!! What a great idea! Saves water (good for $, the planet) *and* is guaranteed to be a faster leeching (in that you change the water daily to get the higher-alkalinity residues out- having always-running water would be the fastest way to do this!)
I wonder if there's any detriment to it being saltwater? I live by the beach, it's far easier for me to find safe/hidden water-spots that are saltwater than fresh! For the time being I'll be opening my toilet's basin up to see if the pot fits in there, but I was really just doing a 'tester' pot, I want to make ten+ pots in the coming weeks so will have lots to cure!!

 

[SU2]

Don't use that, use Mineral Oil far safer for a variety of reasons. Myself that is all I would do, after a few good soakings in water I cannot see PH being an issue.

Grimmy

I would've thought vegetable oil would be more 'like kind' than petroleum oil (mineral oil is petrolatum based right?) I wonder if ceramic glazes could just be applied to concrete? Or even if there's plant-safe, glossy paints I could use on the inside.

 

[GrimLore]

Mineral Oil USP(yes the crap you get at the drug store) is a got to if you want oil and no chance of anything feeding on it. It is the recommended oil by the FDA for wood surfaces after cleaning with a Vinegar Water solution to clean and keep them germ free in Commercial and Home applications. Been using that method here on Baking surfaces, cutting blocks, wooden utensils in the kitchen AND other things like bonsai containers and pots - it just works

Grimmy

 

[SU2]

Mineral Oil USP(yes the crap you get at the drug store) is a got to if you want oil and no chance of anything feeding on it. It is the recommended oil by the FDA for wood surfaces after cleaning with a Vinegar Water solution to clean and keep them germ free in Commercial and Home applications. Been using that method here on Baking surfaces, cutting blocks, wooden utensils in the kitchen AND other things like bonsai containers and pots - it just works

Grimmy

That's awesome, thanks a ton I use vinegar and baking soda as my go-to's for a majority of cleaning projects, sounds like mineral oil is a pretty fitting item to add to my general arsenal (had always thought it was essentially a more viscous petroleum jelly, so figured it would be toxic for plants/life, but your having done it successfully is all I need to hear, will give it a shot on my 1st pot!)

My biggest concern is how long it'd last, would this be applied every time you potted something into the container? Surely it doesn't 'stick around' like an actual glaze/poly would..

 

[jeanluc83]

I would curious about how much it really effected the pH of the substrate. If you are using a inorganic substrate and water frequently I can't imagine it would have all that much of an effect.

What about using paint on the inside of the pot. Maybe some Drylok or something similar. If you stop a half inch or so from the top edge you would not see it once the tree is potted.

 

[GrimLore]

My biggest concern is how long it'd last, would this be applied every time you potted something into the container? Surely it doesn't 'stick around' like an actual glaze/poly would..

Looking at that pot I would say 4 tablespoons on a rag rubbed in would penetrate and such good. First time do it twice - it won't rinse off easily, you would have to use a degreaser to break it up and that would probably not remove a lot of it. Let's just say once soaked in it lasts a long time just like when applied to wood.

Grimmy

 

[Tieball]

Are concrete pots really heavy? Just empty......I'm just imagining a slab of concrete, like a patio paver, that probably weighs 50-60 pounds all by itself without substrate, tree, and water added.

I’ve seen a lot of concrete pots that weather really well. I don’t know if it’s called patina when it’s concrete.

 

[jeanluc83]

Are concrete pots really heavy?

It would depend on the concrete used. When I was in college there was a concrete canoe competition. As part of the mix they added micro spheres, little glass balls filled with air. The cured concrete would float in water kind of like pumice.

 

[Tieball]

It would depend on the concrete used. When I was in college there was a concrete canoe competition. As part of the mix they added micro spheres, little glass balls filled with air. The cured concrete would float in water kind of like pumice.

Now that’s cool. Thanks.

 

[SU2]

I would curious about how much it really effected the pH of the substrate. If you are using a inorganic substrate and water frequently I can't imagine it would have all that much of an effect.

What about using paint on the inside of the pot. Maybe some Drylok or something similar. If you stop a half inch or so from the top edge you would not see it once the tree is potted.

Yeah I'm curious as well, I don't know I just know that even 1yr-cured cement still has an alkaline pH and that bougies (which comprise most of my collection) like acidic conditions, and as I'm starting to get better at shallower pots my pot-surface//substrate-volume ratio increases - so given that I'm looking to start 'mass producing' these I want to be sure beforehand, have peace of mind! (I'm intending to get *all* of my trees into DIY cement pots, that's scores of bougies so just want to be sure before such an undertaking! Have only made a few pots so far, and only used one of them so far)

 

[SU2]

Looking at that pot I would say 4 tablespoons on a rag rubbed in would penetrate and such good. First time do it twice - it won't rinse off easily, you would have to use a degreaser to break it up and that would probably not remove a lot of it. Let's just say once soaked in it lasts a long time just like when applied to wood.

Grimmy

I'd just never have guessed *mineral oil* was OK for this, not toxic to plants! I don't doubt you, in fact I'm kinda stuck between that and a solid (paint, glaze, poly's, etc) right now, you seem very keen on the stuff though which has me leaning that way!!

 

[sparklemotion]

I'd just never have guessed *mineral oil* was OK for this, not toxic to plants!

Mineral oil is sold as a laxative. Not that that makes it totally safe for plants, but people most definitely drink it. I would trust mineral oil to be in contact with roots much more than any paint/stain/urethane product.

Just don't get it confused with mineral spirits.

 

[cbroad]

Horticultural oil is mineral oil so it must be somewhat safe for plants, and honestly, I spray it on the soil too...

 

[Anthony]

You could just soak your pots and at the end of 4 to 6 weeks ---------- test the ph of the
water.

Concrete pots are fun to make and plastic ice cream containers make great shapes, as
do many plastic shapes.
You can make very dense bodies that are non porous or porous bodies [ which we use for
Japanese black pines ]

You can also purchase concrete colours, I believe the max is 10 % of your mix.

Can also be white cement or gray cement or tile grouting.

Why not take a walk on the beach and find other containers.
On our side the sea purges itself of coral shapes, often nice basin
shapes that grow seagrapes [ from seed ] well.

Or hardstones that are easy to carve.
Good Day
Anthony

 

[GrimLore]

I'd just never have guessed *mineral oil* was OK for this, not toxic to plants!

It's not a guess honest. I use a vinegar solution to sanitize/clean all pottery and follow it up with a good coat of USP Mineral Oil. Been doing it for years and I guarantee every clay pot I have stored right now has been treated that way.

Why?

It is the recommended way to clean and keep wood surfaces in restaurants by the FDA. Also, been using it on all cutting boards, wooden kitchen utensils, and baking surfaces.

It is non-toxic, clear, and tasteless.

Grimmy