1. I came across a lot of recipes that didn't use sand (just cement, moss and perlite/vermiculite). Is it best to always use sand for strength or can it be left off for smaller items (let's say a small pot) but is better to use in larger projects (let's say a large trough)? I use peat, perlite and portland 1-1-1 for all my hypertufa, curing correctly will give you the best strenght. For very large containers ( 3ft long) i would add concrete fibers. But the key is to strenght is curing. Sand makes it heavy!

2. Along the same lines as #1... does it make any difference as to using sand when it comes to shape. Example: Are curved or freeform shapes lack strength (vs. squares, rectangles) and as such can benefit from sand regardless of the project's size or does it matter? Again Curing is the key, keep the project damp for 3 weeks, do not cure when temps are below 50o F , do no let it dry for 3 weeks, I do not use sand in any of my projects.

3. Are there any guidelines as to wall/bottom thickness based on the size of the project? Obviously if the project is a planter then the larger the planter the more soil it's going to hold which could make it quite heavy? I'm thinking of doing a trough that is approx 3-1/2'L x 2'W x 1-1/2'H and want to be sure I have an appropriate thickness. Is there a point at which you have to consider adding concrete strengthening fibers or something like chicken wire for strength?

I would consider adding fibers to this project . I have made one similar and the wall thickness was 1 1/2" +- thick, this type of planter you should find a place to display and then fill with soil, do not try to move with the soil in the planter. It will be very heavy. Again proper curing is key to sucess.

4. I would also like to raise my trough up off the ground which means a lot of the weight will come down on the bottom. Should I have a thicker bottom to ensure the weight of the soil is supported or does it matter? I have my large hypertufa on a wood frame, on two 4x4 posts. The bottom has support , to answer your question - 1 1/2" to 2" thick is ok

5. If I use plastic (like a garbage bag) as the means to release the hypertufa from the mold is the plastic enough or does plastic still have to be sprayed with cooking oil? No

6. For curing I read that that item should be wrapped in plastic for the first 24 to 48 hours to get the item to set to the point it can be taken out of the mold. ( yes) Does it have to be sprayed during this time or is wrapping it in the plastic enough? ( keep it moist at all times) When it comes time to removing it from the mold to finish curing is the item left open to the air (in the shade) for this period or is it re-wrapped ( rewrapped) and left to sit or should it be placed in water for the approx 4 weeks (or at least sprayed/hosed down everyday)? Keep it moist for 3 weeks. Smaller containers can be submerged in water as a method of curing, this is a big pot, if you had a really big container filled with water that would work, but really not needed. Just wrap in garbage bag , open the bag every couple days and spray with water, cloes the bag. Repeat!

You did not ask this , however when curring is done it would be ok to rinse the excess cement residue off the planter before planting. If it were a smaller planter this in when youwould soak in a tub. I do thhis before I plant.

7. Does the length of time it's left to cure depend on the thickness of the walls/bottom? ( it could take longer) I think I read on average it's about 4 weeks to cure. ( 28days) Is that for a certain thickness? Google cement curing - 28 days is the time needed to cure cement. 4 weeks would be more than enought time. Most people cant wait !

8. Along the lines of #7... along with my trough I want to make a couple solid supports ( from hypertufa?) to raise it off the ground (almost like the footings/supports you would use under a raised deck). Given these will be solid as opposed to something like a trough or pot are there guidelines for drying/curing based on the thickenss of these or is it the same as a pot? (3 weeks works for these also )

9. Does anyone have any ideas on how to make a freeform mold? Once I get my first trough done I would like to create a pot that is kidney shaped but don't know the best way to construct a mold. ( Dig a hole in the ground, ) I'm in zone 5b. Is there anything I should add to the recipe to make sure it can survive cold winters with frost and ice or should I just seal it? No

No need to seal, I hate to be repetative, but proper curing is the key. I have over 70 pots of various sixes in my garden, several stay outside all year, for many years. Note---- They do not last forever, they weahter, crack a little , ocassionaly fall apart, but for the most part last may years.

Mike

my blog with photos

Thank you so much for this very detailed answer Mike!!! I really appreciate it! I didn't get a chance to try any hypertufa last year because of the sweltering summer we had. I couldn't be outside for more than ten minutes at a time so I postponed my project until this year (hoping for a more reasonable summer). :-) The timing of your reply is perfect! I can start to get everything ready for when it gets warm enough to do this. :-)

Thanks again!!

Karen