Dry Sanding Techniques:
One method of being most efficient in your finish sanding proceedure is to do all of your sanding up to the final coats with a 220 to 320 grit no-load type of sandpaper.
First, let’s go through a few definitions:
Scuff Sanding: This is a very light sanding procedure that quickly takes down any high spots in the finish. Be aware though that this sanding is not intended to take down the low, shiny spots on your finish.
Level-Sanding: This sanding is used after there has been several build coats of lacquer. This is probably the hardest sanding method for the beginner to master because the goal is to eliminate all low shiny spots, while being careful not to sand “through” the finish into bare wood.
Sandpapers used for the dry-sanding methods are available in very fine grits – in fact much finer than you will want to use for this discussion. I would not use a Fre-Cut dry-sanding paper finer than say 320 grit, as the finer papers clog up quite a bit and it can become very frustrating to change the paper so often.
You will notice small hard buildups start to form on the surface of the paper as your paper ages. These lumps can cause a lot of damage and place deep scratches in the finish – not a good thing.
Start out with 320 or even a 220 grit sandpaper. You will find that this cuts through the lacquer coats adequately, and even though you will discover sanding scratches from the coarser paper to appear in the finish, these scratches will melt away and disapper upon subsequent finish coats.
If you feel that you want to use a finer sand-paper (finer than the 320 grit), be sure to use the P-graded, gold-coated aluminum-oxide type. You will find that this paper will minimize any clogging problems that may develop.
Dry sanding can be very successful using either a sanding block, by hand – and as you gain experience you can cut even faster by utilizing a power random-orbital sander. To minimize the clogging problems with the electric sanders, you should step down a grit to minimize clogging problems and finish build-up on the surface of the paper. Start out by trying 220 grit in your sander, and possibly go as fine as 320, but not any finer.
Dry-Sanding by Level-Sanding is done several times during the finish-building stage. There is no set rule as to the number of level-sanding procedures required because that depends of several factors such as number of coats sprayed during an operation, the thickness of the coats and the dry-time between the coats.
I usually go through between 3 and 4 level-sanding procedures before the final wet coat(s) are applied. When you are first starting out with finish sanding, it is sometimes beneficial to do a level sanding about half-way through the build process, as this will minimize the sand-through possiblities.
You also will need to do one just before the final wet coat though. Again, do not be alarmed by the scratches resulting from 400, 320 or even 220 grit-sanding. You will find that when the next coat(s) of lacquer are sprayed, these scratches will melt into the entire finish as a whole, and they will disappear.
Even though we have not touched upon the wet-sanding procedure, this is a very important step in the finishing process as well and it is usually done on the final, cured lacquer finish, just before the final buffing of the finish.