It is now about a year and a half since I made that big barrel of lime putty. It has been sitting outside, in a frost free area, with a constant layer of about ten gallons of water on top.

I have had to move the barrel, and (hooray!) I now have some time to get back into fresco and sgraffito. I transferred the putty into six, five gallon pails. Some observations:

1) The smell is wonderful, I couldn't figure out what is was that was so interesting, then I recognised the smell of corn tortillas! Thats right, mexican corn is soaked in lime and that is why the tortillas have a floral smell, unlike say corn on the cob.
2) the bottom of the barrel lime was more 'cheesy' in texture, and not as 'creamy' as when freshly made. The cheesy putty fluffs up to cream lime when you whisk it. I think the important point is that the weight of 400 lbs of putty, and additional 100 lbs of loose water on top, is what compacted the lime - I don't think that 5 gallon pails are big enough for this effect. If you are going to make lime, make a big batch.

3) one of the important things about the type N lime high calcite lime that I use is that it is "air classified" - this is important. WHen the freshly claved lime comes off the line, an air curtain makes sure that only the very fine powder becomes 'classified'or filtered out - any heavier unburnt bits or impurities fall through to the general lime.

4) the suitability of lime for fresco should be by what Harry Francis calls the blotting paper test. Apparently lime salesmen use to do this to show the quality of the putty. Spread slaked putty like a thin layer of peanut butter over blotting paper (I used several sheets of newspaper), WHat should happen is that the putty will hold enough water so that it does not immediately crack and break. An unsuitable lime will spit out all the water immediately. Of course it will crack and break as it dries(cures) and shrinks becuase we have not added any fine sand. Then the high calcite part is that specks of magnesium could cause different expansion in an exterior fresco exposed to heavy frost and moisture(not too likely at $100 plus per sq foot!).