>
> I am having a hell of a time getting the
>intonaco smooth as glass. What is it i am doing
>wrong? I was able to do it once in one of my
>earlier attempts, but i had no marble so i ended
>up just giving it a shot with soap stone dust
>for that try, but for some reason i havn't been
>able to get it smooth with marble. I sift my
>marble through a window screen, my mixture is
>about half and half, but it seems to be too
>gritty to get smooth. I'm also using a cheap
>trowel at the moment, but i don't think that is
>the heart of my problem. Any help on surface
>preparation? Painting on the glass surface is a "tricky thing" it requires quite a bit of experience with fresco as well as plaster. Mainly due to it being incredibly smoothe (dogh...) your paints hve to be thinner, pigments finelly ground and the painting should be very "presize" and much faster. As you apply layers of paint you close the pores in plaster and it happens faster with glass-like surface.
I personaly do not like very much marble dust since it looks to me that plaster locks up faster with it as well as it is harder to bring to a glass surface.
Achieving a glass surface:
This a subject of a demonstration rather than typing, but a few pointers may help you.
Intonaco is applied in two layers with 10-15 minutes interval. First layer (left sand finished) is a regular intonaco (wetness) second layer is slitely "fatter", this is the layer that gets smooth.
You have to bring this layer to a smooth finish as fas as you can without overtrowelling. let is set (it will have a matte look when set and the finger will not dent it) at this time you pass the trowel (wet the edge of the trovel a little) with pressure a few times (do not overtrowel and make sure you wipe trowel after each pass so it is very clean) it should be very very smooth but will have a few pitholes. give it a few minutes and take a little of pure lime on the trovel and spread it fast over the entire surface - that will fill it and turn the plaster into glass.
Main thing is understanding the moisture and the right timing to do all that. (this part must be demonstrated)
also too much trowelling of the set (ready to paint) plaster will lock it and will make the paints "slide" and paint will not take.
another thing is as you paint on regular surface especially at the beginning (experience wise) you will mess the skin of the plaster, or start paint when the plaster is too wet, what we do during classes is smooth-press it back with the trowel - works quite well.
also (Gary please adjust your "conduit - file" on me)
you can polish (press) the painting at the end with the trowel however it might not always give you the result you are after and depends on your experience.
> Another short curiosity if i may. - I have
>often heard that it is not the paint that sinks
>into the plaster, but that rather through the
>process of carbonization it is actually carbon
>crystals that form over the pigments and lock
>them in. Are you supposed to be able to see this
>upon close inspection?
with a microscope, i suppose... imagine the pond... with a slight ice crust over it in the morning...
or less poetic: stirr some lime into a bucket of water and leave it over night - you will see lime crust shining on the top - this is as thick as it gets.
