How To Use The Drywall Flat Boxes
The drywall flat boxes is a must have tool for any full time taper, but it could be handy for anyone redoing their basement or have a fair size project.
Their are different sizes and lengths of boxes ranging from 7" to 12" in length, and the high tops are wider holding up to 30% more mud. The drywall flat boxes are used to finish coat recessed joints, butt joints, and drywall beads.
Applying The First Coat
We apply two coats of mud with our drywall box, starting with the 10" box. Attach the box to the box handle with the two twist on screws. Fill up the box with the pump till it over flows a little. Change the dial in the front that adjust amount of mud applied by the box, I call the first coat a prefill coat, not much mud is needed. Apply the box to the wall in a quick motion, and then apply pressure on the handle to kept the box on the wall. Run down the wall with the box till you get close to the other end or run out of mud. Use the brake handle on the back on the box handle to hold the box steady when moving to the wall, also use the brake when meeting together for a smooth finish. Make sure to clean off any chunckies that may interfere with the box blade.
First Coating The Butt Joints
Once we are done running the flat joints, we are going to run the two sides of the butt joints. This method of doing butt joints is the best that there is, your butts will always be flat. Little scratches in the mud don't matter as much when doing the sides of the butt on the walls only, because the wall butts are going to get a final hand coat. We also do the two sides on the ceiling butts, and since those are not finish hand coated it is imperative that your coat its of good quality
Applying The Second Coat
MAKE SURE TO ROUGH SAND BEFORE MOVING ONTO SECOND COAT.
The second coat is much more important than the first one. This is you have to be much more picky, looking for pin holes, scratches, and other imperfections. We also use SunLight Dish soap in our mud for the second coat, about 1/2 cup to a 5 gallon bucket of finishing coating mud. The soap really helps eliminating the pin holes since we are only applying 2 coats of mud. Also the second coat should be done with a box larger then the first one to cover over the previous coat. We use the 12" box after running the 10" box on the first coat. If you have to run the box back and forth 3 or 4 times on the same flat to get it perfect, then that's what you have to do. If your box is leaving scratches in the mud, clean the box blade with your finger.
Second Coating The Butt Joints
Once the flats are all coated, we move onto applying the second coat of mud to the butt joints. The second time around coating the butt joints we only apply mud to the middle, instead of on the 2 sides. This step should mostly cover the entire tape on the butt joint, but don't worry if there's a little showing thru the mud as we apply a last and final coat to the butt joint with the hawk and trowel (CLICK HERE TO FIND OUT HOW). So at this stage it don't really matter if you have a little scratch in the mud, it can be left behind for the final hand coating. Using this method I promise your butt joints will be flat and not flash when painted.