>Some of the colors didn't adhere to the intonaco
>layer. The lime / sand mixture was 40-60, and
>though it took a long time for the layer to dry
>and lay my traced pounce drawing on the surface
>( about 2 hours! ),

The mix was way-too-wet for that, try 4-5 parts lime putty to 8 parts sand. No water! It might be a little difficult to mix but after about 20 min of mixing it should be like butter.

>I finally was able to do so
>and begin painting. I first tried to lay in
>some of the shadows and darks with transparent
>earth colors ( umbers, bohemian green earth )
>etc., but some of them didn't carbonize and
>after two days of drying, the pigment flaked off
>when rubbed lightly with my finger, especially
>the browns. Some colors 'took' ok, the more
>dye-like pigments,

Colors should be "die-like", not as thin as ink, but thin enough to run freely from the brush. The depth of the tone achieved by layers - not by the thinkness (of paint). The depth is in underpainting (umber or verdaccio).

In any case you should wait at least a week before you can call it dry (not just two days)
Also colors will dry with a different speed as well as the color of plaster itself will be changing from grayish to white unevenly and for over a week. This will result in-a-bit-of-a-mess in looks of the fresco. DO NOT WORRY IN ABOUT A WEEK COLORS WILL PULL TOGETHER NATURALY! The plaster has to dry, that is it.

look for steps at:
http://FrescoSchool.com

>but the chaulkier ones just
>seemed to dry on top. I don't think that the
>lime surface had "locked up" yet, so something
>else happened.

When mix is "too wet", by the time it becomes "paintable" it very much could be already "locked" especially if you use construction lime, the one that is sold in powdered form in bags - type "S". high content of magnesium in it added for quick setting - hence the name is "S" (stands for "special"), If you are to use bagged limes from general places - look for type "N" (normal). However those limes are not ment for fresco painting.

You would find a whole lot of difference using Italian Lime Fresco Putty from:
http://truefresco.com/frescoshoppe
(it is not a "sales pitch" for what it is - this lime is produced specificaly for fresco painting)

>Anyway, when I sprayed the dry
>painting with a garden hose, all the pigments
>peeled away. This has been a great setback for
>me, after months of research, materials
>gathering, expense, etc. A failed painting
>doesn't bother me so much, but a failed process
>stops me cold; I don't know how to go on and do
>it right.

Take our workshop. At our Los Angeles location we offer classes from one to five days starting at $295 (all materials included)

http://www.truefresco.com/workshop/west_coast_fresco_workshops.html