Not a tufa expert but Have dealt with the desert and cement/stucco/mortar...
It sounds like you don't like to mist and cover?
It is possible in the desert for the moisture in a batch to evaporate prior to the cement cure process and thus you have weaker cement. There is an exact ratio of h20 that cement needs. Extra water during the initial mixing causes severe loss of strength. But if you use the proper proportions (of which I think a good tufa mix like cookie dough is on the dry side of the correct ratio) of cement and water and let it set up for say 18 hours then you can mist or add water and bag to insure that the evaporation loss in minimized and this doesn't cause over watering because the basic structure is already set.
Is is quite common for a good stucco job in the hotter months to include a 3 times a day hose down for several days. This varies alot by wind/humidity/wall thickness/surface area/sun etc.
Also in my opinion using such a dry tufa mix that allows us to mold things by hand makes it hard to insure that each blob adheres to the prior blob. If you shake it to much you might get good consolidation but also slumping of your work.
You might want to try a complete mold both inside and out and then make a wetter pour able mixture that you can tamp and shake and bang on the side to get air bubbles out and insure a homogeneous casting followed by a slow drying process for 7 days and then you might have better luck with cracks. Fibers and latex admixes would help with strength also.
I have also been reading that you can use latex paint as part of say 25% of your water addition and its like a colorant and admix.

I just mixed up a tufa batch using 2 parts sand, 2 parts cement, 3 parts perlite, and finally got to add the 2 parts peat. Also a quart of latex paint in the water and lots of fibers. mixed the fibers in the dry.. works much better IMHO. Paint didn't color things much but it did smell. Added powdered colorants at the end kinda leaving a swirl of color streaks.
Forgot to add the kryptonite and vermiculite!
I can see why you should sift the peat? best method??
And I have to tell you the folks that call this peat should be shot.. Peat is supposed to be decades if not eons old boggy material. There should be no recent twigs and or leaf material to call it peat.
Also this vermiculite is big stuff like 1/4"x1/4" x 1/2" what to do with this stuff?

The original question here was about admix - and so that is the question I will answer. Elkski - you might want to put your questions regarding peat and vermiculite in a new thread so that you can get the answers you need.

Anyway - I have always used admix, Val, but as I have been reading your postings, I was wondering "why" - at least until now. I simply started doing it because the main gurus at the time were advocating it. Never one to question gurus, I simply did it. I don't live in arid place - far from it!!!

As for bagging and misting, I have NEVER done any of that. The gurus were ignored when it came to that!! I mold stuff, let it set up, remove it from setting site, and that is it.

Given that you have items fail only once in a great while, you may decide that admix isn't worth it. On the other hand, the admix isn't terribly pricey - maybe use it for one season....and see what you think.

Keep up the good work - you are quite an inspiration!!!

To wannadanc...thanks. I hate to admit that I'm not one of those that cures forever, because quite frankly, I've had very good luck with projects doing well, especially in the "great northwest". I've never had one project crack, fall apart, etc. Plus, I love to enjoy my things immediately. So much for patience. It's nice to know there's another out there who likes to "keep it simple". To wannadanc, what do you use for an admix. Would like to try it when I come down to Yuma next year. Thanks for your encouragement.

Val - I used "whatever" I came upon that had the word fortifier or bonding agent in its description - and was intended for concrete work. In other words, I have no product loyalty at all. I think I used it in a 1:4 ratio - admix:water - mixing it up ahead of time. If I had underestimated water needed, I just added water to the mud at the end - in other words, the ratio was a VERY rough estimate.

Yippie! you mean Hypertuffa don't need all that misting etc?? as I know with my crete'(not tufa) stuff it would crack in a NY minute if I didn't follow the (learnt here) misting feature. Come to think of it the molded tufa does appear to hold the original 'dampness' longer- So now another question, with no curing how soon after molding can one use a trough to plant plants? or in this case would it be advisable to soak in a water bath as such?
Sorry for all the questions, I know what to expect with crete, tuffa is a little different, not much but it is-and "I don't want to do it if I can't do it right"!!! Wendy

I made this bowl three years ago in Yuma. It has been in the same place for all that time. I never misted or cured it. In fact, it pretty much sat in the sun the first week I made it. There are no cracks or crumblings or anything. It's like a rock by now and it will probably be that way a decade from now. I've misted and cured projects and I've also set them out the first week. It never made much difference for me. Quite frankly, I make so many projects, that if had to mist and cure for a month, I probably wouldn't do it.

{{gwi:67260}}

I tend to agree. In Alabama I dont' worry alot about curing. I cover pieces with plastic and keep them damp for a day or two until they are quite hard. Then I hose them off and put them in the shade. Sometimes I wet them while watering the adjacent garden. I've never had a cracking or crumbling problem except when the temperature unexpectedly dropped into the forties.

Thanks for the thumbs up on this misting thing! I general only mist 'crete for 7 days but it's a messy pain covering and uncovering so this will cut down tremendously on the time doing that. If we have unexpected low temps. with items that don't have 'run-off' I usually turn these over, of course in our climate if it's the on-set of winter I move them to a covered dry place. Thanks again-Wendy

I live in the Northwest and my experience is primarily with concrete and papercrete (though I have also done several projects with hypertoufa) so I really don't know if this will work for you but here is my experience:

It's kind of counter intuitive, because working in a dry climate one would tend to add a bit more water to the mixture, but the LESS water you add, the less likely it is to crack, and the stronger it will be when it dries. I have never read this anywhere but I think that the volume of the water leaves spaces as it dries that cause weakness and cracking in the final project. If I were you I would try using a VERY dry mix even though it may be harder to work with and you will likely have to work faster than you might like. Hope this helps :))

Thank you, terribear. I have always wondered why some projects have cracked in the dry desert climate, and others haven't. I've never had a smaller object crack, so volume must have something to do with it. Yes, even tho dry mix may be harder to work with, I'll try it. Bagging and misting sure hasn't.

Hi Val. There are many more than a few people who don't wait and I am another. This picture is one pot that was planted within days of taking it out of the mold.

{{gwi:67261}}

I use additives if I am thinking about joining pieces but that's it. I had so much trouble with fibers clumping I threw out my entire remaining stock of 12 bags.

About the cracks: I wonder if the water temp might be a factor. If water loss is occurring before the chemical process can start maybe you could heat the water to speed the reaction. (Or vice versa)
Robert

Thanks for the encouragement, Robert. I almost felt guilty because everyone has been talking about misting and curing for weeks on end, and I just never got into that. I tried it for a little while, but it never made any difference. Part of the pleasure of making hypertufa is having a great creation in just a few days. I don't think I could wait a month. I'm like you, I plant immediately and most of the plants thrive...for years. Let's have a thumbs up for simplicity.

I still don't have a handle on why admixes are used. Most folks don't seem to have much trouble with cracking. I too use very dry mixes. I always have a spray bottle of water at hand in case a spot appears to be too dry to bound well with adjacent mix. A key for me is working each amount added into mix already on the mold so it is obvious it all meshes together.
I usually use strengthening fibers, and have no cracking issues. I find they are easy to use and cheap. I wonder about those who say thay are hard to use and clump up. I use a small handful for each large container and spend a minute or two to break fibers apart. One person's comment about discarding their supply of twelve bags of fibers for that reason is surprising.
After all my years making and having classes (hundreds of containers), I am still working from my fourth bag of fibers.
Misting and covering are good things because the mix should cure slowly to assure maximum properties, but I don't over do it. I cover pieces with plastic for several days keeping the piece damp--more days when it is hot and dry-then after they are hard and I have done finishing work, I put them in the shade and hose them off ocassionaly.
Any "added work" of using fibers and the effort of misting to keep pieces damp are not a problem for me. I am not in a big hurry.

Hi Fred, yep I did it, I tossed 'em. It really is no big deal I got a great bargain from the local batch plant so I was only out a few bucks. They even gave me a 50 pound bag of calcium chloride.

Note: Investigations have shown that a two per cent addition of calcium chloride has equal cure strength at 50F as plain concrete has at 70F. Regardless of the temperature or cement type, concrete mixes containing calcium chloride will always have a faster cure rate than plain concrete. The beneficial effects of calcium chloride will be even more pronounced at lower temperatures. The accelerated cure rate measured as final concrete set time can be reduced by two-thirds when two per cent calcium chloride is added - two hours compared to six hours for plain concrete.

I used both a small cement mixer and a hand mixing tub and still had problems with fibers clumping. I guess it's the maverick in me :). Anyway I wasn't too pleased with the "hair" on the surface either and burning them off just didn't cut it. So now I use mostly portland and either perlite or vermiculite, and very little, very fine sand.

Thanks for the info on calcium chloride. I need to try it this winter when it is below 50deg.
Fibers, misting and such---What works and seems easy for one isn't necessarily best for all. That is why I encourage everyone to experiment and learn from failures as well as successes. Above all, be patient and not afraid to try new ideas.

Fred said: "That is why I encourage everyone to experiment and learn from failures as well as successes. Above all, be patient and not afraid to try new ideas"

I said: AMEN BROTHER.

I'm trying to make a "Face" jug using a cement mix. I just finished packing the first stage - the jug bottom. For the jug itself I'll use 1:2:2:1, Portland, vermiculite, perlite,sand. For the character features I'll use Fiber Cement: steel wool incased in cement, as described in Lynn Olson's book - Sculpting with Cement. When assembled I'll apply a slurry of pure portland over the entire piece. Then the hard work begins burnishing the cement to a smooth finish. This is a difficult experiment and there are a thousand ways it could go wrong, therein lies the fun of it all.

Robert

Hi Val I packed the bottom of the jug yesterday, pulled the molds today and added the pieces see my post at:

Here is a link that might be useful: Face jug experiment

Robert and Fred, There are several different kinds of fibers. Some disperse easily and others clump. Their just not worth it for the smaller applications.
An accelerator like calcium chloride is used in construction concrete pours when the temperators dip to 50F. Their talking BIG concrete pours. If you need something fast there's always, "Quikrete" quick-setting cement. It comes in small 5 or 6 lb pails. It sets up in about 15 minutes. Billie

Wow, I really appreciate the advice on admixes. It's so great to know there are fellow "mudders" out there and everyone is truly unique. It's just amazing the knowledge out there.

Robert, I love your planter and can't wait to see the finished project on your sculpture.

Just wanted to let you know that I just got back to Oregon from snowbirding in Yuma, Arizona. Checked out all my tufa projects and there wasn't one crack. There were spots of dirt, moss and other spots of antiquity, but no cracks. So, I know definitely that any cracking is limited to the dry environment. So, I may look into adding an admix when I'm in the desert. Also, making a drier mix. But, now that I'm in Oregon and the humidity is higher, it's taking forever for this stuff to harden enough to wire brush. Ugh! Nothing is every perfect, and that's why we love hypertufa. Thumbs up to the primitive look.