Marmorino & Stucco application
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GETTING A STRAIGHT EDGE ON CORNERS
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.
GETTING INTO HARD TO TROWEL AREAS
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 sometimes essential with Marmorino. LIghtly sanding it with a soft sanding sponge will smooth out any undesired microtextures and give more depth and mottling to the wall. You're not really sanding. Instead you're kind of compressing it a little and giving it a little accent here and there. 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 Marmorino is done perfectly and you have the whole thing smoothed out, you can unmask it and walk away. More often than not there will be something you might have to fix. Fixing burnished Marmorino is a little tricky. This requires wetting down the area you are about to work on, then very gently sand the wall. You can then burnish it with a trwel as it is still wet. Sometimes whole walls in this manner to give it a different quality of sheen and 'feather' it out making it more natural. Wet sanding Marmorino is a little more difficult than doing it with Veneziano, because you have to fight the sand of the Marmorino.
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.
Unlike Veneziano. do not try to use electric sander with Marmorino.