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I had a bad experience today with Plaster Weld by Larsen during an ongoing kitchen remodel.
In theory, a bonding agent is recommended when repairing and then skim coating an older plaster wall prior to repainting. Based on a number of internet articles, I chose Plaster Weld as the bonding agent. It bonded to the cleaned and repaired wall just fine, but after 24 hours when I applied the skim coat (in this case, drying topping compound), the Plaster Weld re-wet completely, losing all film integrity. The instructions state that you can apply wet plaster to the Plaster Weld in just one hour after application of the Plaster Weld, so 24 hours seemed adequate.
The skim coat and the surface of the plaster weld flowed together, turned pink (the color of Plaster Weld) and proceeded to slump on the wall as if the skim coat had been applied to a greased surface.
I spent the rest of the day cleaning both topping compound and Plaster weld off the wall - not a happy way to spend my time. I will now skim coat the old fashioned way - directly onto the cleaned and sanded original surface.
There is a lot of refurbishing of plaster in older homes here in Louisville, so I was initially surprised when no local supplier carried Plaster Weld. Now I know why.
By the way, the Plaster Weld held just fine to the old paint - While I could remove a portion of it by washing with strong cleaner and water, I had to remove all the old paint in order to get all the Plaster Weld completely off the wall.