I don't get why Ian the plasterer does not recommend using silica sand? The key is a 'sharp' sand - it must have lots of hard, sharp, jagged edges - this is where the strength is once they are compacted. Sharp silica sand is easily available from the sandblasting suppliers and the mason yards. Also, apparently, the silica is partially dissolved by the lime - and silicates are the strongest thing you can add to concrete. Flyash and pozzolans are silicates.

Pure silica is glass.

I have white marble sand, black 'slag' sand, dolomite sand, playground 'river'sand, ground polyester sand, none of them would be as good as silica or 'mason's' sand. For real high end lime mortar the silica sand is partially milled, like a grindstone type thing.

there are few reasons, and those are mainly due to painting, not the strenght...

Silica - speeds up the setting of the lime hence shrinks your painting time, colors "slide" when painting on silica. (it is also part of the reason why it is not quite possible to work on dolomitic - magnesium lime)

secondly, althow it is "edgy" and sharp, high calcium lime does not like to stick to it (meaning layers)

Garry, i know that you use regular lime (type S - with a lot of magnesium) so you do not have "sticking problem", however magnesium + silica give tenfold of the problems in painting and after all it is about the painting - isn't it?

more later, was out of the door...

I would be most interested in your source for all this?

It flys in the face of what every stonemason, plaster mason, and brick mason has been doing in USA, Canada and the UK for the past 200 years. I work with restoration masons all the time.

How can an inert substance like 'glass' speed up the 'cure' -absorbing Carbon Dioxide - of lime?

What possible difference can less than 1% magnesium oxide cause? If it is higher - it can form into tiny little chunks - but not a problem with air classified lime - and also pockets of high concentration could cause different 'freeze thaw' - only a problem if your fresco is going outside in freezing wet weather.

I would be interested in seeing a chemical data sheet on your lime before I ordered any - is this available?

>I would be most interested in your source for
>all this?
>
>It flys in the face of what every stonemason,
>plaster mason, and brick mason has been doing in
>USA, Canada and the UK for the past 200 years. I
>work with restoration masons all the time.

Gary you miss my point again - i do not argue with you about masons using materials they use. I am talking about painting on the materials they use and serfaces those materials give...

We have experimented with silica (sandblast) sand - easily found and clean.

1) mix is rather watery then "fat"
2) layers (arriccio + intonaco) do not stick as well as in other sands.
3) plaster sets (stops accepting paint) faster causing latter layers "slide" and not to stick.
Pouzzoli Red is one of the picments used in fresco for its color advised NOT to be painted over with other colors because it locks the plaster.

here is what I remember from other resources i read in relation to silica - you perhaps can clue me in it better since it is about plastering - hydrated lime is what we need to use for fresco, "hydrolic lime" is what is quite good for plasterers because it is like cement (will set under water) some of the people I know also say that dolomitic (high magnesium) lime putty will set under water when mixed with silica or even other sands.

from italian book - add a little terracota since it has clay which has for the plaster to set faster.

>How can an inert substance like 'glass' speed up
>the 'cure' -absorbing Carbon Dioxide - of lime?
>
>What possible difference can less than 1%
>magnesium oxide cause? If it is higher - it can
>form into tiny little chunks - but not a problem
>with air classified lime - and also pockets of
>high concentration could cause different 'freeze
>thaw' - only a problem if your fresco is going
>outside in freezing wet weather.

I never said less than 1% 90-95% of calsium is a realistic number.

>I would be interested in seeing a chemical data
>sheet on your lime before I ordered any - is
>this available?

no datasheet is not available - only about 7 years of using it...

I suggest you question this knowledge Ilia.

The big question is =what exact kind of sand are you using? What size is it and where does it come from?

Hydraulic lime expands in water - it never cures in the sense you are saying, but you can see how this might be useful underwater or for brick mortar - not for fresco.

I currently have all the new books on Michelangelo for a sculpture project. I also have all the reference materials on the Mexican fresco artists. I also have the book on the Ajanta cave frescoes, and a lot of old plastering books.

This fresco material and technique you describe was rejected by Michelangelo - it dried too slow and there was effloresence - he used a lime putty (based on travertino) - and he added pozzolans (which are silicates) and brick dust. Vasari also recommends this technique. Michelangelo also differs in technique from you in that he does a lot of preparatory sketches and drawings - but he still created as he went along. As he went along, he first abandoned sinopia, by the time he got to the lunettes - he abandoned cartoons. And they also found a lot of secco areas from the hand of Michelangelo too.

Diego Rivera also used a dolomite lime putty, from the Mayan sources, washed mason's sand and imported french white cement. I have a video of him working - he too seems to work fairly freely. He did use fresco pigments, and probably brushes, imported from France.

So the two most famous works of fresco - the Sistine Chapel and the Rivera murals did not use the methods or materials you describe. It does not make your way wrong - but the point is there are so many ways - careful of falling into a trap. Making fresco seem like some lost, magical art, with exotic imported materials, and strange languages, only serves to drive people away - or back to their watercolors, acrylic and oils - or stuck in the mystique, rather than the art.

Also, involved in conservation as I am, no conservator in the world would allow a lime putty anywhere near their project without a chemical analysis.

"Making fresco seem like some lost, magical art, with exotic imported materials, and strange languages, only serves to drive people away - or back to their watercolors, acrylic and oils - or stuck in the mystique, rather than the art."

Maybe this is too harsh Ilia. You are not the first European to come to America and offer up 'the old school' on a plate. The trouble is you have to look at the market - what it wants is 'Fresco Painting for Dummies' - thats what you have to deliver - in a box, everything you need to make your first fresco

ANd there is no technical reason why this should not be so. You already have video footage. You can print up already prepared cartoons. You can slap a thin layer of lime putty onto nearly anything. It may become the art of the swimming pool and patio - but so what - thats the market, and thats the starting point.

Gary you misunderstood me,

silica is bad that is all I am saying.

Bad because if someone uses it and then runs into trouble - there is no way back for that person to much work gone down the drain, who will want to try again...

and there is nothing more difficult in buying "whashed plaster sand" from home depot and sifting it through window screen for the intonaco (skim coat) and arriccio (float coat)then getting a bag of sandblasting sand from the same home depot

So if I, you, someone else provides a foolproof method that works then student has a success and if later he/she runs into the trouble they know that they had it working.

and about european materials - the first thing I say at my workshops is that the main thing is to develop common material base! First thing architect or developer asks is where will you get your materials and who is your backup in case the first source fails...

and do not use our lime for experiments - no need to waste money. Go to Cafe al Fresco, read Gary's post about making lime putty - there is nothing wrong with it. Later on when you get more familiar with the technique then get Italian stuff. and there is correct (calcium) lime putty in the US for instance in Virginia. I did not try it myself since the cost is about the same and what is the difference where to buy as long as you get the right stuff.

Take our shop - it does not sell in a year more than one workshop uses. Why people do not know what to look for, so they are not looking at all.

So the problem is not finding stuff, the problem is that everyone has a different suggestion of what to look for. So people rightfully think that "lets wait untill these guys get their story strait"

So let me get this straight - you are using what my home depot calls 'playground sand' - for like kid's sandboxes etc. I have never seen 'mason's' sand there - masons don't go to home depot - except to buy Martha Stewart potpourri

Ilia - I am serious about doing some kits. I am already working on some carving kits. Do you have any idea how huge the market is just for kids/teen/adult craft kits - on christian themes alone? Kids got to ahve projects for the summer camps, especially the bible/church ones.

Contact me off list if you are interested in contributing / co-marketing etc.

our home depot sells plaster sand that is called just that "plaster sand" it comes in plastic 50lb bags it is a bit too yellow for me but makes rockhard plaster, so i go to stone suplier he has whiter one.

I am building vbulletin based fresco dedicated forum it has subscribtions and public areas I am going to ask you if you want to participate when the structure is ready.

and yes we shall talk about marketing things...

really good thread guys!
much appreciate these discussions on the fundamentals......
finding out about materials is intriguing,and the problems have been solved with variations in different localities.

the split has ocurred in many countries with the old lime traditions being handed on.but they still exist in the middle east,italy,france etc

noyice how you have to worry about what sand it is from home depot.......like trying to make cakes or bread from all in one packet ingredients from a supermarket.

these discussions get us more and more to a total handa-on
ability. and gary has always explored and been so inventive.

look forward to a trip over to usa some time to catch up and swap
some good times - joe