First of all, thank you all - I have looked so long for a place to find information and to ask questions, and this is the best there is...Please - two questions: I just cant seem to find a definitive answer with re to applying any natural finish, e.g. venetian plaster, limewash, etc, over modern "plastic" paints. I know that the lime needs key, but how to achieve this is the problem. I have wondered if I need to rough up the wall with very coarse sandpaper, or even put up a fine wire and then a layer of plaster. Second question: I have also seen lots of info on this site about what lime putty to use. I seem to gather that it needs to be low magnesium, but some people differ...?? I am just afraid of it cracking off my walls; imperfections in color and everything else, as far as I'm concerned, will just add character, but vp on the floor is not character:) Please help - thanks! Maria

well, there are many materials available for that.

Your question is very broad...

for example many premixed plasters contain acrylic additives to make them easier to apply and for better adhesion to common walls (drywall and stuff)

variations of lime plaster finishes are more of a "construction" type of finish meaning used more often then lets say fresco (you can even find some in Home Depot, sure that is not a "real stuff" there) and designed to work well with common materials. Many manufactirers have a special "base coat" plaster that they offer...

Check Joe's http://adicolor.com for descriptions

for example here:
http://adicolor.com/Adicolor%20-%20Step%20By%20Step%20~%20Lime%20Plasters.htm

fresco is a different story though...

thanks for your reply...I have actually been involved with vp for a long time now. I do NOT want to use anything from Home Depot, etc - and in fact dont want to use anything artifical - no polymers, acrylics, etc. So I was wondering if anyone knows what natural substance would provide key for the vp to adhere to. And this is why I wondered if I needed, in addition, to score up the wall, or sand it, etc. I hope this distinction helps.

also - with re to my second question regarding the lime putty - I know that there was quite a long thread going here discussing U.S. lime putties vs European. Was there a consensus? Is there a good manufacturer here, or do I need to order from Europe? Thanks again.

nope, we still import lime putty
you can find aged fresco lime putty here:

http://FrescoShop.com

as for the "VP" - expended metal (fuond in Home Depot or masonry yard) for base coat is ideal, but adds expence.
a shortcut is using developed base coat materials.

we import a line of italian plasters (that have acrilic binders in a base coat) for our VP projects - dont sell them though.

however you can ask Mitch this question - go to FrescoShop and use contact form:)

You are mixing up a number of terms here. Is venetian plaster a 'paint' or a 'plaster' to you? It is typically marketed today as a paint, heavily thickened with fillers, but called a plaster.

So will paint stick to paint? Yes, no, sometimes

Will plaster stick to plaster? Usually, sometimes no

Will plaster stick to paint - almost never

Will paint stick to plaster - usually, unless it is fresh lime.

Cracking is common in paint, because the fillers are so fine (usually calcium carbonate and mica). Cracking is also caused in plaster by fillers too fine, placed too thick, or too much water

Lime putty is simply a chemical called calcium hydroxide. The issue is if there are 'contaminants'. Very rarely, in lime mean't for fertilising cattle fields, there is a higher level of magnesium (cattle need magnesium) and this will cause a problem for outdoor fresco, in the frost, maybe. The guy that was so against 'magnesium' in lime was also the 'expert' who threw all his sand away because a raccoon had walked across it in the night.

I am one the ones who considers 'Venetian' Plaster to be a plaster - it is the final coat (not including beeswax) of a three (or four) coat lime plaster process using darbies, plumb bobs, and a polishing trowel. The final product is as smooth as a piece of glass and is called a "level 5" or "level 6" finish by architects and designers. It is rarely seen today outside of resorts, casinos, etc. It is an expensive wall mean't to last two hundred years, and is often mistaken for a sheet of marble or stone. A true lime plaster wall should not be painted for one year (recarbonation, etc.) so this caused all sorts of grief in out hurryup culture - by coloring the plaster with variations, and then sealing with beeswax (still allows to breathe) you have a wall which is attractive and resists household stains, etc. It has to be done properly because it is glossy or semi gloss - it will show every dip and wave around - at the worst time - the finishing steps. The gloss also gives the depth and illusion of stone.

So you have to decide do you want to learn how to plaster, or do you want to learn to to make paint sort of look like plaster. Usually it is the customer who gets to decide - but in Canada and the US, there are so few true plasterworks to inspire, and too much industry marketing emphasising the now and immediate.

Mason's of all types used to consider a 100 year life span as the goal - now I constantly see construction products with a "lifetime' warranty - 25 years.

Hi Gary,
I guess I might have provided you with a bit more context, so that you see that I'm not the ordinary DIY-er looking for Home Depot products. I'm not a mason, either, or a chemist or architect, but something in between.

I have been researching vp for over six years now, ironically, bc I first saw it on a DIY show on tv - and at that time, of course, in the US, there was next to nothing available, in the way of products or info. Before that time, even, I was very familiar with vp from my family in Europe, where of course the technique has been used for centuries, and is in that area very traditional.

So...when I speak of vp, I do not mean paint. You may be familiar with the name - I just finished up Mike Wye's course in England, in fact, bc I wanted to learn the "old" European way. I know a great deal with re to vp, about the many coats and their application, about pigment, about how lime changes chemically, etc., etc. What I cant seem to find info on - I think bc mostly everyone is OK with using the "fake" products - is how to apply the REAL technique to my lathe and plaster 1910 walls that have unfortunately through the years been covered in commercial paints.

So you see, that's where I am. Hence my questions about how can I prep my walls, for a REAL application of vp, hopefully by not using some "fake" primer or adhesive. I hope this helps, and again, thank you for all your time.

Maria

OK - now I understand - we are talking plasterer to plasterer - but you need some help with someone who has done 'Do Overs", escpecially in lime plaster. Luckily, I do have some experience in this area, on 1910 and 1913 walls.

If the wall was not an existing three coat plaster wall, you have to make sure it can handle the weight of the new (10 to 15 lbs a sq ft - 4foot by 8 foot = 400 lbs). If it cannot - which is probably the case in this day of wood studs and drywall renovations/"improvements", then your options are limited.

If it is existing plaster, you must use like a light hatchet/axe to 'hack back' to a rough finish. You can tell from the sound of the plaster whether it is strong - if it is not, these areas of the scratchcoat will have to be repaired with wire and scratchcoat. Then it is a simple matter of plumb bobbing your straight vertical lines, you build up like a 'train track' for the darby to follow. More on this technique if you need it. The then final trowel coat, which is thin and consistent, so it is as flat as your second coat. The polish with the trowel at just the right stage and it begins to shine. It feels like cool, sensuous skin and the lime smells wonderful.

Over drywall, cement blocks, etc., is much more of a problem as you already know. It is difficult without assessing each situation - and you can still be wrong. If the cheap ass clients won't go for rebuilding the wall or ceiling, the only thing left is a skim coat. But you see you don't have your handy little 'train tracks' here - and there are probably 1 in 100 trowel workers who could make perfect flat. You can't see it for a start. You can use concrete bonder to help the plaster adhere. You can use a plastic 1/4 inch mesh too, from the stucco store, in areas likely to be cracked with vibration. Both these techniques require a thicker skim coat, and it is difficult to trowel without the latex bonder 'polluting' the lime surface. You will know right away when you hit latex -its almost like being on rollerblades, and then hitting a patch of chewing gum (not that you could get me on rollerblades!). So the practical answer to make a happy client with skim coat is to make sure it is colorful and flat luster finish - both these elements distract the eye.

If you are your own client - this is the chance to learn from outside the theory. Believe me - it is worth the effort. A perfect wall, in the right home - a pure white lime putty finish with glittery white carrerra marble dust worked into the final stage, then sealed with potassium silicate one year later - every time you entered a room such as this you would smile.

Maria,

I could give you a couple of suggestions but am not quite sure how "pure" you are trying to stay.

Are you interested in fixing what is there and simply apply an authentic "finish" or do you want to restore it to original?

For example 1910 residential homes did not use metal lath. So if you are willing to go that route then you might as well use a modern binder over the paint (if it is sound) possiby a sanded lime basecoat and then use your venitian products over that.

As far as lime is concerned you should be able to use the type "S" lime available at home depot for the the base coat.

The problems with the type S lime is that it does not hold color very well (which is not important in a base coat) and many who are inexperenced with it experience cracking. The cracking can be overcome since the plaster in your 1910 home is lime plaster.

Thom

I did advise Maria to go to Murals plus forum, but that post seems lost.

As I understand it the guy who does Illia's plastering has met a fellow from N.Ireland called Paul, who is more than willing to help with Marias question.

Go to the forum and ask your question there, believe me I am not detracting from those on this site just trying to do you a favour.

Hello - I replied to your post of Jun 2, but I'm wondering if you ever got it - could you tell me again what you wanted to tell me? And how do I get in touch with Ilia about that (Irish?) person who you thought would be willing to help with some questions? Thanks! Maria

Hi Maria,

I have not used sandpaper before on my finishes, but I've heard in here:

www.venetianplasternewyork.com

that this could be done with extreme care.