The components of any mixture will vary from region to region and from garden to garden. The exact composition will be dependent upon: - The types of materials which are available in the area; - The local growing conditions and, - The type of plant material. The term "soil" is really somewhat of a misnomer. The components normally used to create a good potting mixture are, in fact, soilless. They are designed to provide an ideal environment for root growth. In creating this "perfect" environment we also create a few problems for ourselves. First, it should be obvious to even a rank beginner that the rocky concoction described below will dry out a heck of a lock quicker than the sticky black potting soil which most people have been using for years. Secondly, most of the components in the soil mix really are one kind of "rock" or another, which means there is virtually no nutrients in a properly prepared bonsai potting mix. Both of these aspects are unfortunate, but necessary if our soil mixture is to have the success we hope for.

shazaam wins the prize. They were looking at the addition of sand sized calcined clay as a water retention additive. I would imagine as a substitute for actual sand. Turface is a much coarser calcined clay and as such the calcibed clay used in this study is not analogous. And this is why you have to carefully read the study and not just the abstract. :edit: what's really interesting is they were getting the effect of about 30% sand with half the material. And let's remember the reason growers add sand to container media is because it facilitates even wetting of the media. It is not for increased drainage like some people think. This post was edited by nil13 on Fri, Feb 28, 14 at 12:02

fleur do not be discouraged by failures of peat. more on that in a moment. I will start by stating I have no exp with hypertufa. That is what led me here. However as most things I do, I try to think of all things untried from a start on the foundation of physics (career habit). I think your suggested mix will be ok with 1 additional additive, a plasticizer. My first thought is with such a large percentage of perlite your mold will have a sever case of crumbling due to the excessive expanding and contracting of the perlite material. This type of activity is only 1 of many cuases for cement base products to crack but probably the most common. I would try starting with very small batches for something simple like maybe some coasters for the coffee table. Just add some felt or cork to the bottom for protection of the table. In my search on the web I have found tons of various lightweight cement ideas but the Hypertufa seems to be the most practical for home use. There are a lot of other lightweights out there but they employ special manufacturing technics that are not possible/practical for small scale use. On your problems with the peat. I have read that the best way to prepare the peat is to completely break it up and soak it in water for a few minutes then squeeze the excess water out before adding to the mix. Not sure how peat is sold in your area but for me it is sold in compressed blocks and if I took a small clump and tossed it in water it would simply float for hours. I have to literally pulverize it before use. I recall the first time I used peat was for a mulch and the water just flowed right off the bed. So I had to go thru the whole bed and rake it all out. I learned it wasn't good for mulch so I mixed it in the compost pile, it did wonders there. I don't mean to be harsh but I find it difficult to think you have done it all correctly when so many people have succeeded. Keep in mind curing is critical and curing all depends on both ambient temp and humidity plus the moister content of the mix. In my area the only successful crack free cement projects I have seen is when the project is continuously kept moist for several days. The real tragedy in that is I rarely see that done. I work in the construction field and most houses I go to have cracks in the driveways and often in the foundation yet the contractors seem to just consider it normal. I personally would never buy a home with foundation cracks when it is only a few days old.

Thank you, ToxCrusadr! Your reminder of the fact that DG are solid, unchanged particles rather than the porous end product of expanded shale gave me my "DUH/I'm a moron" moment. Regarding expanded shale research: I enjoyed a brief (grant-sponsored, part-time) employment at the Tex A&M Urban Solutions Center in Dallas a few recent years ago. I was very fortunate to spend a brief time involved in soil sciences. However, my experience with this discipline was limited to soil fertility. Having said that, I feel that some of their non-fertility amendment based research (corporation funded grants) and subsequent results are often an effort in ridiculous predictability. My own extreme and annoyingly sarcastic example would be "would an ice cube retain its crystalline structure in an oven or a freezer". Therefore, I hope that the general gardener would not decide to attempt a successful garden using expanded shale alone. My understanding of the affects of various amendments to soil structure is limited to classroom lecture, persistent questions and personal experimentation. I am truly grateful for the chance to get advice from many varied angles.