| I've asked this question of literally dozens of contractors over the years and frankly have never gotten a straight answer. While they all have a preference as to what they use, none of them have EVER been able to give me a concrete answer on what specifically. In fact, you've probably noticed that on many of them the labels are identical.
Funny thing: There's a similar mystery between "Topping" and "Joint Compound". I know contractors who use one of the two exclusively for all projects...so apparently there's not that much of a difference.
Now, that having all been said, I'll be very curious to see if someone in the know has a concrete answer...
PS. As for me, I use powder mix joint compound for everything. |