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Vasari Plaster & Stucco application is simple even though there are many long explanations. Most people figure out how it works within several minutes just by playing around with the product on a few sample boards. You don't have to be a professional or an artist to get excellent results. After working with the plaster on a sample board or wall, you'll get a feel for it. One important thing to keep in mind is that the details of preparation can be as important as the plaster application itself. Simply follow the instructions below or watch our videos, and if any questions come up, please search our blogs, revisit our videos or email us.

Veneziano plaster is smooth and creamy in it's consistsancy. It can have a soft, silky finish with little sheen or be burnished to a high shine. It compliments both traditional and modern settings depending on how applied. Veneziano is made with lime and powdered marble and can be very durable, especially with a sealer or wax. We can make your plaster more durable by special request if going in very high traffic areas. Color combinations and creative styles are unlimited. Our plasters are very environmentally friendly, healthy and its qualities will improve with time.  Vasari's hypo-allergenic products will breath with your home absorbing moisture and naturally prevent mold or mildew growth.




  • well primed new sheetrock with a high grade primer
  • previously existing latex paint (as long as it's not peeling off the wall)
  • well primed wood (or well primed anything)
  • unsealed cementatious coatings
  • unsealed concrete
  • cement boards, cement blocks, and most dense 'non-flakey' or dusty surfaces





  • floors
  • countertops
  • unprimed joint compound
  • raw sheetrock
  • pools
  • oil based surfaces
  • unprimed geso


Veneziano is mostly used on interiors but can also be applied on exteriors. We recommend sealing it outside. You can even use it in shower stalls (over Marmorino, Stucco  or cement for durability).  




Depending on how you apply it, a 5 gallon bucket will cover about 300 square feet. That's both coats included. If you're going over previous texture, like orange peel, you'lll get 200 square feet per 5 gallons. If you're doing it really thin and tight, you might get up to 600 square feet  or more per 5 gallons over a very smooth surface.




There are several brands of synthetic 'Venetian Plaster 'on the market commonly found in paint and home improvement stores. Our products are not comparable. Our plasters feel like real stone because it's made from stone. The other synthetic products feel synthetic like plastic. There are lots of other natural wall finishes products out there. They all work a little different. So point is -- try to forget everything you ever learned about other products. We don't like using spatulas and tiny trowels to do large rooms. We don't like sanding all day to with fine sand paper to make it look like something.  If you're a contractor, like a drywaller, stucco guy or concrete finisher, please, forget what you know.  This is completely different...and easier.


If applying Veneziano on drywall, for new construction, drywall or gypsum board should be1/2" to 5/8" thick. This is standard thickness. The drywall should be taped at least at level 4 or 5 for Veneziano. If you're doing thicker coats, you can get away with level 3. This means there were three passes of joint compound on the tape joint. If you still don't understand - just don't have bumpy tape joint. Otherwise, it can be applied to other similar surfaces including 2 coats of Marmorino. For expanding metal lathe / cement (or other types of lathe) we recommend that the product be used as a finish coat only, and that the base coats be of Marmorino, Stucco or smoothly finished cement brown coat.

If a wall is lightly textured (like orange peel), you can use 2 coats if you put the first on thick. If you want to polish it and make it super smooth, you should do 3 coats. If a wall is very textured, consider  2 coats of Marmorino first or extra layers of Veneziano. You can smooth out walls with texture / joint compound, too, but don't forget you'll need extensive sanding and one coat of primer afterward, so it might be more cost effective to use more coats of the plaster.

Any trim around the wall should ideally be stained, varnished, lacquered or finished already. The reason for this is that when trim is worked on; chances are the painter will stain the plaster or over spray lacquer, regardless of how well they mask it. This can leave a messy line between the wall and trim, especially if the plaster will be unsealed. It's harder to install trim on a textured / plastered wall.


On new construction, you have to prime. On remodels, where there is normal latex paint, you don't have to prime. Our plasters will stick to previous paint, as long as it's not damaged.

Use a water based / acrylic / latex high grade primer to prime the drywall. Primer should be used on other substrates, such as wood, glass, metal or almost anything that latex primer will bond to. Not only do you want the primer to adhere extremely well to the wall, but if there is ever a leak from plumbing or rain, the primer will create a modest barrier between the plaster and the leak. Mask before you prime. (See best masking practices on page 3) Also, when using most stain blocking primers in smaller confined areas with little ventilation, consider wearing a respirator (not a dust mask). Some primers have styrene, carbonized chlorine and ammonia. Ask your paint store for low VOC primer. With Veneziano, good priming is crucial, especially on new construction. Since you will be applying thin layers of plaster, make sure there is absolutely no taping mud/gypsum mud showing through. This will crackle or discolor  the plaster and make for very poor adherence. In fact, priming twice is best.

After priming, if you want, you can lightly scuff the walls for a little more 'tooth'.


Light orange peel texture is fine as long as you use have a thick first layer or three layers of plaster instead of two (only burnish on the third coat). For thicker texture, you should skim coat drywall with plaster/mud, then sand until the walls are reasonably smooth. For thicker 'cottage cheese' walls, sand with at least 80-grit or lower sandpaper, preferably with an orbital sander. Then dust off (clean) and prime the walls with an above-mentioned primer. You can skip priming if the walls are relatively new and are well painted. Just remember to scuff walls to give a little extra tooth to the plaster. Remember that even if the existing walls aren't perfect or totally smooth, and you're not going for a shiney smooth finish with plaster, your walls will still look natural and the way they're supposed to be.

Use your best judgement on applying over really old walls in bad shape. Try a small area first. Let it dry and make sure it sticks. Veneziano will breath with the wall. It won't allow for mold growth.


If there is wallpaper, strip it, then prime the wall. If you are willing to play it less safe; be certain that it is firmly attached to the wall before applying plaster over it. Find a corner of the wallpaper and try to strip it dry. If it comes off with ease, is old and peeling, or has several layers it is best to strip it. If the wallpaper is on the ceiling; pay special attention. It is always best to strip the ceiling of wallpaper; gravity will not be your friend. If the wallpaper adheres well to the wall, prime it with an oil-based primer, such as Zinser's or Killz oil based primers (these primers can be messy and hard to clean). If it bubble when it dries, cut out all the bubbled paper out of the wall and re-prime that spot. Afterwards, prime with latex primer so the plaster can stick to that. Consult your local paint store for further advice.  Make really sure that you explain to them what you want to do as long as there is latex on the last coat before the plaster. In any case, stripping wallpaper is the best practice.


Always mask before priming and plastering. Good masking will result in a razor sharp line between the plaster and anything adjacent. When masking, be sure to buy the right tape. Blue tape is the best. Don't use low tack blue tape. It generally falls off trim under its own weight. White tape is too sticky and can either leave a sticky residue on the trim or tear off the paint or varnish to which it sticks. If using white tape, make sure it's not exposed to the sun, otherwise it will over stick to the trim. On remodels, sometimes the wood is very lightly varnished and even blue tape can peel off the finish. In this case, use low tack blue tape. When masking, use a hand masker that applies paper directly to the tape. Mask about 1/32" from the adjasent substrate (expose a little of the trim). Make sure when plastering not to get too much plaster on the tape. This will make it difficult to remove the tape later. 



There are 2 ways of plastering. One, with a hawk and a trowel, and the other is with a pan and a knife (usually for drywallers). We prefer hawk and trowels.

The hawk is the pallette or square with which you hold your plaster. And the trowel is the thing you apply the plaster with on the wall. (Just making sure.)

You can buy trowels, hawks and anything else you need from most major hardware stores.

Make sure you have the appropriate equipment:

-small spatulas (or something that will get into hard to reach areas)

-box of latex gloves


-goggles  / glasses (to avoid getting plaster in your eyes)

-spray bottle of water (for cleaning and extending open time)

-fine sanding sponge for sanding unburnished plaster, smoothing out corners and bullnoses.

-respirator if you plan to work with dry goods or dust from sanding

-little 2" spatula to get into smaller nooks and crannies


The trowel is the most important piece of equipment on your job. It can be a source of great frustration or a bad job if it's not perfect, so pay attention...

As said, you can use trowel from any major hardware store. Most trowels will work fine. Some pros would differ with this statement. The most important thing is to have a super smooth and straight edge. When you buy a trowel run your finger down the edge to make sure it doesn't have any dings or nics. Also, look down the edge of the trowel to make sure it's not bowed or wavey. All trowels are made a little diffferent, so make sure you're getting a good one.

Stainless steel trowels are preferred, but you can also use the non-stainless. Stainless steel won't rust and most importantly, they will leave less potential grey marks as a result of the metal rubbing off a little when burnishing.

When you get a trowel, you have to sand down the edges with 220 grit or less. You can also use a fine file. Sand it until you can run your finger down the edge and feel nothing. Even sand the top edge of the trowel. This will make difference. Don't use a mechanical grinder on the edge. It can damage it. You would go through this method even with special Venetian plaster trowels.

You can grind down the corners a little with a grinder or on concrete. This will eliminate any potential lines on the plaster left from sharp corners of the trowel. Pool trowels work well, but you need a smaller tool to get into corners.

Don't buy trowels that are manufactured with the metal 'grain' running perpindicular to the length of the trowel. These type of trowels are very hard to smooth out.

You'll be applying Veneziano with tight thin strokes, so any imperfections in the trowels can leave some very obvious lines. Prevent any dings at all times. You can usually get rid of imperfections with fine metal files.

Again, make sure your trowel is perfect. Before you do the last coat, always test it on a sample board to make sure it's not leaving any lines or scratches.

Some recommended trowels are Marshalltown and Taskforce (pool trowel) available at larger hardware stores.  Kobalt is not so good for Veneziano. Buy whatever fits best, wether it's size, steel or the grip.


16" -  if you're a pro and have more than 200 square feet to do and have a good shoulder.

12"-14" - If you're doing less then 200 square feet and you can take your time or if you have a modest shoulder.

10" or less - If you're doing a smaller intricate application with lots of variation or just need to get into tight areas.

Ultimately, just get what feels most comfortable. We can sell you a trowel, but you should definitely check the stores first. They pretty much have what we have. They have all the other tools and accessories you will need, too.




IMPORTANTDo this on at least a 2 square foot sample board before committing to the real thing.  It's easy once you figured it out.                

Veneziano can be applied soft and subtle for an elegant larger scale application, or it can applied with a polished marble sheen. Check out other possibilities of applications in artistic techniques videos and text.

Our plasters  dry much lighter then when wet. Don't be surprised when opening the bucket.



1. Trowel on a thin buttery coat of plaster. Let it completely dry. It might take overnight.

2. On your dried plaster coat, apply thinner compressed strokes of plaster. Again you can make it very subtle, or polish it for more drama. Apply thin, compressed, scraped coats of product, burnishing  (polishing with the edge of your  trowel) the plaster as it dries. OR you can apply slightly creamier coats and not burnishing it at all. Burnish it only when the plaster is at a clay like consistancy-not sticky and not totally dry. Let each area set up a little before you apply another thin layer and burnish it.

3. When the second coat is totally dry, you can unmask, leave it alone, or you can wax it or seal it. For the unburnished less dramatic method, we recommend sanding it with a worn fine sanding sponge or something similar, then wiping the excess dust off with a damp rag. This will slightly sand it, feathering out any unwanted microtexture, and this will help accent the wall with giving more color variation. You can sand out corners and other troubled areas with a a sanding sponge, 600 grit sand paper or #0000 steel wool.

4. For the really polished  and smooth version, we recommend applying three coats, very thinly , only burnishing the last coat as you plaster the wall. Always let coats completely dry before the next.


Getting the plaster off the hawk is easy is easy after about 20 minutes of practice.  First scoop a bit of plaster from the bucket onto the hawk. There are special tools for that that in the drywall or concrete section of a hardware store. Or you can use a spatula knife or whatever works.

The first time the hawk is used, it will react a little with the aluminum of the hawk. It will feel very slippery for a few minutes then stay on with no problems.

Sometimes plaster will be thinner than usual. Sometimes almost soupy. Deeper colors have more tint. In fact up to 3-4 quarts of tint per 5 gallon bucket. When we mix it, it can take some time to settle or thicken for easier use. If the plaster is soupy, put on very small amounts on the hawk. Like this it will air dry a little and be easier to work with. Take only small slivers of the plaster with your trowel. This will take longer, but it will be less messy. Another trick is to have a small paint roller and roll on small sections and trowel them out. You can make it look identical to a normal trowel method.

Finally getting the plaster on the hawk. Don't scrape it off the hawk. Cream it off the top compressing the plaster a little at the same time. You can take little or lots of the hawk depending on what you're plastering. Don't scoop the plaster from the hawk. This is what most beginners do. Just compress it and skim it from the top not scraping the metal of the hawk.  New trowels will be slippery at first with  the plaster. After a few minutes the plaster will stick better to the metal of the trowel, like the hawk. It's like 'priming the metal'.

1st coat
If you're going for a more subtle look without much variation and polish, spread the first coat about 1/32 to 1/8" of an inch thick over on the wall. Work top to bottom. Trowel it like butter. Always trowel at an angle. Never lay it flat. Whatever texture you end up with on the first coat will determine much of final variation of color  on your finished product. If you want texture and more interest, give the first coat a little texture here and there. As it starts to dry, you can go back and mess with it a little- adding here, taking away there. As it dries, it will tend to tear a little on your trowel. Spraying water on the plaster will help with this issue. Your second coat will will act differently from your first.

Use smaller tools or even cut pieces of plastic to get into tight areas. The best way is adding water to a little plaster and making a thick slurry. You can then brush on the slurry to areas, like tight door jams, pipes, wires, covers, etc.

If you want the wall to be polished like marble, apply your first coat about 1/32" on an inch thick. Make it as flat as you can. Flatten out more textured areas as it dries spraying with water the areas you flatten out.  For a perfect smooth polished wall do three coats of plaster. Do the second coat like you did your first. You'll notice that this time you'll be able to he wall compress flatter layers into your first coat. Don't try burnishing it here. You'll see that the wall will become very smooth and flat allowing for very thin last coat, which for convenience sake we'll call the...

2nd coat
For the more subtle elegant look, apply the plaster top to bottom at about a 1/32" of an inch. You'll have areas where you scraped it on, and areas slightly thicker.  Don't apply it like joint compound. It's not a texture mud. You can apply it in layers, allowing each layer to set up a little, like clay, before you apply more on top. You can scrape on some layers and leave others a little creamier.  You can also leave some of the first coat exposed here and there. The layering technique will give you more depth and variation, even if it's subtle one. As it starts to dry, you can compress the plaster with the edge of your clean trowel holding it at an angle. This is burnishing. Do this lightly once or twice. The more you do this the more dramatic and polished your wall will become. So don't over do it if your going for a quiet classic look.

For the high polished  burnished look, apply very thin compressed layers as you last coat. When you first do this, the layers will dry withing seconds. If you apply another paper thin layer over that area, you'll have more open time, letting the plaster dry slower. Continue layering super thin layers of plaster on top of one another. You need very little material on your trowel as you do this. Burnish as you go. Compress it with the egde of your trowel at an angle. You'll start seeing a high polish right away. This is were your trowel has to be perfectly smooth and clean, otherwise you'll have scratches. Keep adding thin layers. Each layer will add more variation and depth of color when burnished.  Burnished areas will be darker than the unburnished areas.   If you get scratches as you go, apply slightly thicker plaster layers on the scratch, let it set up, then apply another layer over that, then burnish. Again, make sure your trowel is perfectly smooth. You can come back when the wall is mostly dry, and give it a last burnish for that extra pop.

As you will learn on your sample, if your over burnish it when it's still a little tacky or wet, it can crack or tear. If you keep burnishing with too much force, it can also tear. Make sure you apply plaster wet on wet so you don't get lines where you stopped. Do the whole wall at once. If it's a large area, mist water on the areas where you stopped, without letting it streak down the walls. That way you have more time to work with.


Before or during your last coat, you can run a small brush with plaster on it in the corners of the tape and the wall. You can also smear your finger (while always wearing gloves) against the tape and edge of the plaster. This insures getting a clean professional line when you unmask it.


If you're trying to get into nooks and crannies, use a smaller tool.  Get a spackling knife or even a square of plastic from a milk jug...whatever works. Use your fingers. Sometimes you'll find special tools for this at the hardware store. Try painting the plaster on with a brush in those tighter spots.

Use care or a corner trowel for corners. Use a flexible rubber 'half-moon' trowel or your hands for bullnoses.


If you feel that you're done, you can unmask it.  If you have chunks of dried plaster on the tape, you'll have a harder time and you might rip out a few fragments of plaster along the way.

A good idea is to mist the tape with water softening the plaster a little. Also,  it's not a bad idea to gently score the tape line with a razor before unmasking. Careful you don't scratch the wood if doing this.


Sanding is not essential. It does however make it easy to fix things and give more pop to to the plaster. It makes the most difference on unburnishedd Veneziano. This done with a fine slightly worn sanding sponge or similar. You're not really sanding. Instead you're kind of compressing it a little and giving it more accent and depth of color. The more the plaster was burnished lightly, the more 'pop' you'll have when you sand. You don't have to scrub hard...just a few times in the same area. It feathers out imperfections and get rid of little bits of plaster sticking up. Sand over bullnoses and corners.  Stop if your scratching the plaster. It means that you sanding implement is still too hard and gritty.

Make sure to wipe the dust when you're done. If you have areas that you're not happy with even after it dries, try wetting the area with a spray bottle (or whatever) and gently sand the area in question. The plaster will soften a little and the sanding will take off a very thin top layer of the plaster. Try this first on your sample board. Do this very gently and slowly at first. You can wipe out any 'mud' that you made on the wall with a rag. Let it dry and see what happens before you do larger sections.

If your burnished Veneziano is done perfectly and you have the whole thing polished out, you can unmask it and walk away. More often than not there will be something you might have to fix. Fixing burnished Veneziano is a little tricky. You can get a little more pop from Veneziano by sanding it with 600 grit or higher sanding paper. Do this with a large sanding block.  At your own risk, you can use a mechanical sander. Don't use orbital sanders. If there's a spot that need attention try wetting the area, and wet sanding with the sand paper. If you time just right, you first take off a thin layer if the area, and as it starting to set up, the sand paper will start polishing the area and feathering it out with the sorounding plaster with no evidence of what happen. Sometimes people do whole walls in this manner to give it a different quality of sheen and 'feather' it out making it more natural. This is sometimes done when colors are combined to give a more natural combination. You can burnish the wet sanded spots with your trowel, too.

For more pop on unburnished Venziano, if sanding doesn't work, you can wet the wall and burnish it with your trowel. After it's dry, if you still need more, you sand sand the area and ot will be darker and more varied.

The physics of this whole wet sanding process is exactly the same for polishing marble and granite. This is a very touchy process, so make sure you practice. It's a good thing to know if you have to patch a burnished wall. It's sometimes the only way to fix it.

WARNING: Electric sanders and water is a dangerous combination. Do this at your own risk.





There are natural sealer and synthetic sealers. Read more on sealers in our maintenance and sealers section.


Are used when you don't need waterproofing protection but a mild resistance against minor dirt, stains or dust. These sealers include natural beeswax and soap. When you seal plaster, it's often much harder to repair the plaster and some of the environmentsl aspects are lost.. Don't use these on exteriors, shower stalls or more 'extreme' areas. These sealers  prevent any possible 'rubbing off' of really dark tinted colors off the wall or  lime dust refusing to get off the wall.

Natural beeswax can be applied with a rag, applying small amounts then buffing it out right after. Beaswax is a very traditional way of sealing plaster only on interiors. You can use clear beaswax, or try different colors for more variation and depth (mostly for accent areas). Wax gives it great dirt and minor stain protection. Wax is very easy to reapply any time. Wax / colored wax is great to on polished plaster to give it a more uniform sheen, covering all the areas which weren't burnished. When waxing Veneziano, it's easy to get streaks. Dampen a soft rag with Lacquer Thinner and go over the wall polishing it at the same time. This will give you a mirror like sheen and also take away any accidental heavier spots of wax.

The biggest downside with wax is that it stinks. It smells really bad. Once it dries the odor completely disappears withing hours and there's no off gassing. Wax has solvents. You have to wear a respirator and gloves when applying.

Colored waxes go really well over colors you want to deepen in tone, like deep reds.

We recommend BriWax. Try getting the Toluene free version for less odor. Unfinished furniture stores almost always carry the stuff (as it's great for raw wood). Ace Hardware always carries it.

Some waxes will darken your plaster too much, so apply clear wax first, then your colored wax. You can even color your own waxes out of the clear wax and even add pearlescents and metallic powders.

There are lots of waxes out there. Our customers are always finding new products we haven't tried yet.

And as always, try the sample board first. Wax is a real committment. Once it's on, its on. If you ever have to go over wax, you have to scuff / sand the whole wall with 180 or lower sanding paper until every inch has plenty of 'tooth'. You can replaster it right on top, or you can prime it, paint it, or whatever you need. If the wax was very heavy, scrub it off first with a rag and lacquer thinner.

Soap is great and easy traditional way of sealing plasters in interiors. It takes away the 'dustyness' of the plaster and give a little more deepening of color. It also feathers out the variation.  Here's an interesting and inexpensive way to make your own soap sealers:  buy unscented, uncolored pure castille liquid soap. These totally natural soaps are hard to find in most stores. The best one (we think) is called Dr. Bronner's Pure Castille Soap. This is available in most natural fancy food stores. Cut it with about half or more with water, and apply it with a rag trying not to let it streak down the wall. Carerfeul going around corners. If you double it up too much, it might darken a little more in those areas. This is a really great way to finish plaster.

Tinting soap doesn't work very well, so don't bother.


You can seal it if it need the waterproofing protection. The downside of sealers is that it's harder to fix or change the wall once you do this. You shoudn't have to do it in whole houses. This is best done in kitchen backsplashes, shower stalls, public areas, some high traffic exteriors, extreme weather exteriors and alike.

We recommend solvent based penetrating sealers. The same ones used for natural stone tile and countertops. These are found at most tile stores. We sell sealer, but it's just as easy to go to the store and get smaller quantities. Make sure you but 'non'enhancing' sealers that won't permanently darken the plaster (unless you want to).

Follow the instructions on the sealer can on how to do this. You can usually wipe our brush it on. For extra protection, do 2 coats.

There are many synthetic sealer products on the market today. Many acrylic and many don't seal as well as they should. So far our favorites are Miracle Sealants 511 Impregnator (or Penetrating Sealer) or Dry Heat products from Australia. Use other sealers at your own discretion. Test them out before you do a large area. Acrylic sealers (and there many) will tend to darken your wall by 5-100%. They will  leave a plastic sheen behind, whereas the solvent based usually are completely invisible. Acrylic sealer on the other hand can significantly improve the durability of a wall, whereas solvent based just give really great water protection.  Sealer technology is always changing and improving. It's a technically complex industry. Try it what you think might work, and as always, on a sample board first.


If the line where you taped wasn't straight or was unmasked with a jagged edge, either wipe clean any excess plaster / paint with a rag and water, score dried edge with a blade.   Add water to the plaster, making a slurry out of it, and dab small ammounts of the plaster with a small brush.

'Double-mask' spots like edges re-tape the area and run your brush or finger along the tape. Double taping means that you masked both sides of the trouble spot exposing only the sliver of the spot. That way, you won't have a smudge or an obvious looking fix.

If the plaster takes on damage, like a major ding or nail hole, simply take the plaster and apply it onto the spot like putty. Even it out level to the wall. Let it dry, and then sand it, or wipe it with a damp rag, or plaster slurry to make it look seamless. Remember to wipe away sealer or wax before doing this. If using an acrylic sealer, sand the area a bit, patch, then re-seal or re-wax.  Try the wet sanding method if your not getting the results you want.

If the plaster drags or peels when burnishing, stop and let the plaster dry a bit more. If this still persists, spray the area lightly with water and try burnishing again. Usually peeling is a result of over-burnishing an area or burnishing when it is too wet. Otherwise, it is an adhesion problem with the wall. Sometimes, the first coat is scraped on and there's not enough plaster for the second coat to adhere and absorb into, crackling or peeling might happen.

Bubbles mean that the base coat is expelling gas. If you mix your own colors, sometimes using an electric drill at high speeds can whip tiny bubbles into the mix. You can usually cut them down by floating them out, or you can reapply another thin coat over the area. Once in a while you get tiny bubbles from minor chemical reaction when certain aspects of the products didn't have a chance to settle out. After a a few days or sometime a few weeks, your plaster should 'settle' and stabilise.

It could be that the plaster was layered much too thick. At some point, the plaster gets too thick and will crack. It's designed to be applied in thinner coats. Another issue may be that the primer was too chalky (cheap product) or the base coat was oil-based instead of acrylic, or there was dust on the wall.

Sometimes, the room or wall was too cold: do not apply plaster in less than 45 degrees Fahrenheit. Another weather related issue is that the plaster can freeze, thaw out and be degraded. The plaster dried too quickly or is too near a heating vent or direct hot sunlight. The base coat sucked the moisture out of the plaster too quickly. Wet the base coat next time.

If after burnishing, if there are undesirable lighter spots that you missed; spray water on the areas and polish them with 600-grit sandpaper, re-burnish the area with a trowel as you go. Small trowels work great for this. 

First try lightly sanding the area with 600-grit sandpaper and wiping it with a damp rag. If this doesn't work try 400-grit sandpaper. If that doesn't do it, wet the area, and repeat the sanding. Be gentle. Wipe with a damp rag afterwards. Then, make the plaster into a slurry by mixing with water. With this slurry, dab the areas with a small brush, or trowel a very thin layer over the area and sand it out when it dries.

This is because the trim is not caulked or the wall and trim are separated. You can prevent this by caulking larger gaps before you start. The smaller gaps can be filled with plaster on the second coat. Often on new construction, wood is not fully dried and the trim shrinks. This is why after a year or two, you see cracks in the caulking of the trim. In older homes you usually don't have to worry too much about this. For newer homes, try taping the trim a little closer to the wall, so if it does move, it's not too obvious of a defect.  Try the 'double taping' where you mask only revealing the sliver of the gap and caulk or plaster it then.

Veneziano is easy to maintain. There's nothing to do unless it needs cleaning. You can wipe it with a damp or even wet cloth. Always try your worn sanding sponge over the area to erase minor dirt, then 400 grit or lower. If it's burnished, you don't want to scratch it with low grit paper. Un-burnished Veneziano, because it's not polished, can take 220 grit or lower. If that doesn't work, just put another skim coat on the area and then sand it. You can also add water to the plaster making a slurry, then dab it on with a brush or rag. If Veneziano is unsealed, do not clean the adjacent trim with oil. If it gets on the plaster, it will discolor. Wipe walls only with water, unless cleaning difficult dirt. If it is sealed with any type of sealer, then you can clean the trim with oil.

If you're applying plaster where you don't intend to have floor trim, make sure you seal the bottom 5 or 6 inches with an invisible non-enhancing stone sealer.

For tougher stained areas, try rubbing the spot out with Lacquer Thinner.