Greetings Packrat,

Thank you for sharing your experiences. This is particularly valuable information in that you have used this method for a long time (12 yrs.) with specific plant species. An inexperienced person could follow your instructions with confidence of positive results.

That being said, you could expand your experiences a bit and gain the gratitude and respect of everyone interested in using hypertufa to make vessels for growing plants. As you are aware, disagreement exists regarding the impact that lime from hypertufa has on plant growth. Some feel the problem is overstated, some think a few hours in water will leach the lime, others support more vigorous treatments, and almost all agree that the plant species is fundamental to the equation. Would you consider conducting a rather limited, controlled experiment that would test the significance of hypertufa lime on the growth of a Crassula species? Of course, there are almost endless variables one could test (different species, different vinegar concentrations, different lengths of treatments, etc.) but it would be exceedingly useful to everyone if you were to contrast plant growth between a control group and a single variable like your standardized vinegar treatment. I would be pleased to help you with an appropriate experiment design to insure the results would be meaningful. At the risk of sounding pretentious, I have considerable experience designing experiment protocols.

Regards,

Ron

The important question would be whether you ever skipped the vinegar treatment and had bad results. This is a relevant question since I haven't used any form of acid (any acid will work, vinegar is just convenient and relatively safe to use) to leach cement products and have not observed a plant problem. Simple rainwater is mildly acidic, free in most places, and good at removing lime. It is also worth noting that lime continues to be produced at the surface of cement-based objects for at least several months.