Tango88: Thanks for the info on the curing process..what a big help for all us new Folks that are wondering if we are doing things correctly.
I have a question for you..I have noticed that when I put my projects in a bath of water there is a film of some sort that gets on them..is this the lime? and what can be done about it....I have also noticed if I don't bathe them and just spray them there is no film..Any ideas???

Myback Garden,

My stuff does that too. You have to change the water every day, or every other day for the lime to leach out properly, when you have your projects in a bath of water. I have three down in my basement right now, and I slip down each morning and change the water.

Jilly

Thanks Jilly : How do you know the lime has been leeched out?..Is there a time frame of any kind...or what do you look for to know the lime has been leached? Thanks Deb

Deb,

I only water cure my 'tufa planters for two or three days before I use them and I haven't had any problems. If you're going to put sensitive plants in your 'tufaware you might want to keep changing the water daily for a week.

peak

I usually keep them in a bath for a week as I have absolutely no idea whether a particular plant is sensitive to lime or not.

Hi Peak, glad to see you are still alive. Looking forward to getting back to the 'tufa trail??

Jilly

Thanks Peakpoet and Jilly..

I'm so glad everyone here shares their information...it really takes a load off the old brain trying to think about it all.. :)

I have no idea what plants are sensitive or not..(I am not a gardner by any means...I am just learning what plants need minimal care because..I seem to kill them all) Not intentionally...it just sorta happens....

Do you mean alpine plants?(I haven't got that far yet..deciding what to put in them..lol making them is about all I can handle at the moment..hahha.

I will be cautious and leave them to bathe for a week/changing the water daily...just in case I'm able to somehow grow a sensitive plant.... :)
Thanks To Both of You for the info

Tango, That's interesting about the mister. Wonder if it's available all over the U.S. or just warmer areas.
Myback garden, There's a film on the item or there's a film on the water? When I put things in a water bath you'll see a film floating on the surface. After changing the water every day for about 3 days the film is gone and the lime is usually leached out. If you're talking about the slimey feeling/film you get on your hands/fingers after you've handled a fresh piece that's actually your skin melting. Yep, I wondered and asked my La Farge rep. Grossed me out! That's why you should wear gloves when handling newly made pieces.
I do the same as Peak, water cure for 2 or 3 days. Then plant any old thing. Welcome back Peak. Billie

That's a good idea Tango--especially where you're at!! ...and here we were the other day having an argument that you had to use aggregate of some kind (including sand as an aggregate) and you're using Portland pure. Why would you be using this application? For smoothness?

They use to sell something at Walmart that was a sort of loosely coiled stiff pvc pipe with a mister on the end of it that sat on the ground and was about as high as a patio chair. You would connect a water hose to it. I've also seen the misters (the small metal device) sold with the drip irrigation systems that you find at Home Depot/Lowes in which you could probably customize your setup but there would be more work to this one.

Tango, didn't you post something about sprinkling baking soda inside of molds to give concrete an aged look? I meant to reply to that one but didn't--now I can't find it at all! Was I hallucinating? I wonder if it's a texture thing only or if the baking soda works chemically??

That posting was "yet another trick fromt the pros" and is on about page 6

Thanks GB. I originally did a search on "tango" and it only pulled up two pages. By doing "tango88" it did three pages and I then found that post in it. I thought their search engine was better than that.

Hey Guys...Took a little digging but I believe the link below shows the "misting" system I'm using. They show quite a few options...the one I have was the "Redi-Mist" cheapo-ready-to-use for about $16 bucks. Their Home Page is http://www.mrdrip.com/. Looks like they can be ordered direct or you may be able to contact them for "the dealer nearest you". Stay cool everybody.

Here is a link that might be useful: Misting Kits & Systems...

Has anyone built Tango's system? Heat is coming, but not for me in foggy SF.

To All,

Is there a good primer on curing? After reading this thread I am having my doubts about this. Here at work we run our cement lined pipe through "curing ovens" which are kept around 120F. The linings have a residence time in the ovens of about 30 min. so they don't dry and crack but the curing process is accelerated enough that we can immediately coat the cement with a layer of asphalt paint.

This discussion thread seems to indicate that cool, humid conditions are better for curing. Can someone point me in the right direction?

I am thinking that I should just let my pots rest in the river by my house for a few days. That may do the trick. Do you need to soak the stepping stones in a water bath too?

Jazz I would love the recipe for that concrete.
This might give me more uses for my barbeque.
Since we cut back on eating meat the poor thing hardly get's used.

Ack!! No, not in the river, ChristineW!

Cement products are not friendly to aquatic life. Knowing how caustic Portland cement is, just THINK how it must feel to a fish or frog. A big plastic tub with the water drained onto your lawn is a better idea.

Mabel

Jazz, crete cures in warm & damp (wet) atmospheres best. Have you all noticed when your tufa is curing it gets warm? The curing produces heat, but once the air around the crete gets below 60F, it cures more noticably slower. The colder it gets, the slower the cure, til it stops altogether. I wondered how warm crete should be for maximum curing time. Must be at 120F. 30 minute cures at 120F???? THAT'S HOT, or is it THAT'S COOL!!!

Jo

Tufa Enough, The recipe for our linings is simply 1025 lbs sand, 525 lbs cement (usually type 5) and 30 gal. of water. That is roughly 2:1 sand/cement ratio by weight and fairly soupy; I don't think we can measure the slump, its got to be greater than 9. We mix this in batches about every 20 minutes.

Jo, understand that a lining in a pipe is only 1/8" to 1/4" thick. 30 minutes in the curing oven gets enough cure/dry to keep paint from blistering due to water under the coating. The cement is fed through a lance with a screw into the pipe as it spins. Once the cement in place the spin speed is increased to about 5 G's (gravitational force) and vibration is applied so the cement is very compacted. (If care is not taken we will spin too long/hard and all the sand migrates out to the pipe surface and the cement rises to the surface of the lining and gets washed away with the laitance. That's bad.) Anyway, your statement about warm, humid conditions for curing is more in line with my concept of cement treatment. My concern arose when Tango88 made a reference to keeping "everything under it cool and moist". I have read enough of Tango88's discussions to know that he is very knowledgeable (sp?) about cement and techniques and coloring and adhesives and molding and ..., so I wanted a bit of guidance concerning curing temps.

I'm casting a pot today on a stainless steel bowl.
I'm going to get it really hot in my barbeque but keep it basted with water and see what happens.
What are the properties of type 5 cement?
I use type 1 mostly and type S when casting over an armature.

Tufa 'Nuff - I'm going to predict that at "really hot" barbeque temperatures your bowl is going to crumble. When the water inside the tufa gets to boiling temperature the steam is going to get out somehow. At least put the bowl in the coolest part of the grill and keep the temp as low as you can. That will be an interesting experiment.

Most barbeques are accompanied by copious amounts of beer. I'm not a drinker so I would probably consume the water and baste with the beer! I could probably make a good slug trap with that yeasty smelling bowl! HA!

As for the characteristics of type 5 cement, I'm afraid I'm ignorant on those details. According to a recent posting in this forum type 5 is resistant to sulfates and is used mostly where the soil is very alkaline. Our pipe is used almost exclusively for potable and waste water mains. I'm would think that most waste streams from general small business and residences are on the high end of the pH scale because we mostly send soapy water down our drains (baths, dishwashers, clothes washers, etc.). I'll ask around here some more to see if there are any other reasons for using type 5. We also keep a hopper full of type 2 for certain customers. I work in Systems Engineering and deal more with computer networks and control systems so, as my friend Forrest Gump says, "I'm not a really smart man..." as far as cement chemistry is concerned. However, it is fun learning.

I Googled on "steam cure cement" (something I had read about recently) and found the Cement Association of Canada website.

"1. Methods that maintain the presence of mixing water in the concrete during the early hardening period. These include ponding or immersion, spraying or fogging, and saturated wet coverings. These methods afford some cooling these through evaporation, which is beneficial in hot weather.

2. Methods that prevent loss of mixing water from the concrete by sealing the surface. This can be done by covering the concrete with impervious paper or plastic sheets, or by applying membrane-forming curing compounds.

3. Methods that accelerate strength gain by supplying heat and additional moisture to the concrete. This is usually accomplished with live steam, heating coils, or electrically heated forms or pads."

It goes on to discuss the three methods in detail.

Here is a link that might be useful: Cement Association of Canada

No steamed tufa for me.
I want mine fried.
Onion rings on the side...and a Coke...no ice:)

Daisy, Thanks for the link; that's good info.

To all: Well, I might have barbequed crow soon! I'll be eating crow, or taking my foot out of my mouth, or whatever the proper expression should be! While asking around here about cement types I came to realize that I have had them backwards. We use type 2 most commonly and type 5 is used for special requests, usually desert type areas overseas, i.e., Middle East. So, I'll admit my mistake and take the consequences but I couldn't leave you all with the wrong info. (Its not likely that you are terribly concerned about pipe linings. It is the use of cement types and their purposes and curing them that got us into this discussion.) You all have been so generous to give information and tips to everyone who asks. I couldn't bear the thought of leaving bad info in this forum that might one day mislead someone.

That all right Jazz we forgive you.
So when are you coming over to take these 15 bags of type 5 I bought yesterday off my hands?:)

Tufaenough, just read about your tufaque and it won't work. It won't explode like regular concrete, but the extreme heat breaks the crystal structure in the crete and makes it as brittle as old stale cake. Been there, done that, but I am still working on heat safe tufa using a secret ingrediant. Perlite and vermiculite is heat safe and the peatmoss allows the steam to escape. I have fired tufa to 1450F and used it for glass molds. It's really cool.

Here is a link that might be useful: tufa under fire

I was only planning to warm it up in the barbecue to the same temperature Jazz mentioned but I got carried away in my explaination.:)
I still plan to test tufa at about 125 degrees.
I'm going to look into those plastic oven bags and see how large they get.

What are you planning to do with the bags? I think your tufaque fire will be higher then 125F. It was 106F at Lake Mead today and they weren't even cooking there yet. You made me think that I should be doing some kiln testing at different temps to see the impact it has on the tufa. This has been my main mission with this. I really want to develop a tufa outdoor woodburning pizza/BBQ oven and maybe even mosaic them. I think we will be in production by the end of summer if it goes well. For a good pizza I need to bring it repeatedly to about 500f. I think 125F will be fine for your tufa. Your won't experience any problems with it as long as it is fully cured.

Jo

I plan to put the wet tufa in the bag then heat it up and let it stew in it's own juices and see what happens.:)
No real reason for it but you never know when you might need a bit of something cured really quick.
I have a salmon on the barbecue right now so the tufa is gonna have to wait.:)

Let us all know your results. That experiment sounds interesting. I am wondering if anyone has ever checked the temperature that concrete gets while curing. Ever notice the heat it produces?

I have never been able to feel any heat from my tufa projects.
POP on the other hand get's down right toasty hot.

Wow!
Next time I'm curing a pot I'll use the dog mister I got at Petsmart! Its suppose to keep the dog cool & comfy in hot weather, but he doesn't like it. I'd finally get some use out of it! It's just a little coiled tube type thing that attaches to a garden hose so I could probably just sort of drape it over my project.
Herself