Plaster Help?
So, as y’all know, Ross finally braved doing a plaster scratch coat. Just a bit.
Now, a week on, when I brush the scratch coat with my hand, it easily becomes loose and sand-sized particles fall to the floor.
Is this normal?
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Sounds like brown coat mix may have dried out too fast. I’d brush it, mist it, skim coat it and see what happens. Old plasterers books I read advocate lengthy–like weeks–of drying final coats. ‘Course that was for a lath-up whole wall new plaster.
I’ll try that, John. Thanks!
Are you sure you have the right amount of clean, washed sand aggregate in the mix? You could have too much.
Michael, I’m using stuff right out of the bag. The instructions say: just mix with water.
If it is Gypsum Wood-Fibered Plaster, you don’t need aggregate. Otherwise, I think you do. I wouldn’t be surprised if there is a toll-free company phone number or a website that might explain what went wrong.
I’m not so sure any of us are qualified to answer this question, Ross. I’d get ahold of somebody at USG or the like. My personal opinion is that your mix is too dry, or it hasn’t been mixed long enough, but what do I know?
More natter from the what-do-I-know camp: it has been crossing my mind that you mentioned a short while back that you got some bags of plaster and then let them sit for a few years until you were ready to dip your toe in plaster, so to speak. I have never used wall plaster but I make plaster molds for ceramics and I know for sure that if I buy a bag of plaster and then let it sit and don’t use it up right away, the plaster sets up more crumbly and bubbly and it takes a higher ratio of plaster to water to achieve a normal pouring thickness. My mold making teacher specifically told us not to let the plaster get old and to keep it in a bin so it didn’t absorb moisture through the bag (we’re talking 25 lb bags of plaster here, it’ll fit into a large dog sized dog food bin). If you’re still using the old plaster, maybe buy a small, new bag of plaster and see if it works better.
Is it the plaster that you did over drywall? Because unfortunately that MAY be why.
Hi, Sabrina!
I didn’t plaster over any drywall.
Oh good! Except that I’m out of ideas now 😀
Hey Ross, Am catching up with your website. I am now living at my new “unlivable” house and am working on it from when I wake up in the morning until I go to sleep at night.
My experience with gypsolite, which is the product that I use for browncoat, is that I scrape off all of the “furry” stuff with a taping knife before applying the finish coat. I use the dry mix drywall compound for the finish coat. Depending on how much I am expecting to cover, I choose the 30,60 or 90 minute dry time. I have learned that it’s easier to add another thin coat than to sand off. I make it as smooth as I can and shave off excess when it is barely set and again when it is dry. Who knows, I may be doing it wrong, but it has always worked for me
I neglected that I use a wide stainless steel taping knife to do the shaving off