Contrary to what most people think, ready-mix joint compound is not
ready to use straight from the bucket. It needs to be mixed for the
compound to spread evenly, which leads to a professional-looking
finishing job with less sanding.
Ready-mix compounds are
available in several versions. At home centers, you’ll find regular and
lightweight all-purpose compounds. At drywall-supply stores, you may
also see taping, topping, and ultralight compounds. I’ve found that
regular-weight all-purpose compound works fine for most
drywall-finishing projects. Lightweight all-purpose compound is a good
option when you have to carry a lot of compound far from the truck, but
it’s softer when dry, which makes it susceptible to damage. Lightweight
compound sands more easily than regular compound, however, so if you’re
new to finishing, it’s worth a try.
Powdered setting compound,
which is mixed with water before use, hardens chemically, making it a
better choice for patching holes, for thick applications, and for the
tape coat. It is also stronger and doesn’t break down with exposure to
water, making it good for bathrooms and other wet areas. Don’t, however,
dump it down the drain when cleaning up.
Most lumberyards and
home centers have setting-type compounds with 45- and 90-minute set
times, but drywall suppliers often have compounds available with set
times from 5 to 210 minutes. The number on the bag is the average time
that it takes for the compound to firm up enough to apply another coat.
This time can vary with temperature and humidity.
Preparing both ready-mix and setting-type compound is an important first step in becoming proficient at drywall finishing.