When to Change your Sandpaper

One of the main contributing factors to the look and feel of a finished project is sanding. In preparation work, sanding is one of the most important steps. This is even the case in-between coats of paint or varnish and many times even after the final coat. No matter when you sand you have to know when it is time to change the sandpaper, as with using sandpaper that is too worn down you will not get the results you want.

How can I tell when it is time to change the sandpaper?

It is time to change the sandpaper when:

1.
The sandpaper becomes clogged with whatever you are sanding, such as wood dust, paint or varnish,

2. The abrasive on the sandpaper gets word down.

Many times you can clear the sandpaper of wood dust or dried paint by using a paint stir stick or a stiff brush and going over the sandpaper. One thing that works well to remove these things off the sandpaper can be an old toothbrush.

Many times when you are sanding finishes that are fresh, sticky balls of the paint or varnish can form on the sandpaper. This is especially the case when sanding the finishes of a water based paint. These can be annoying as they form fast and after you swipe the surface a couple of times. When they form you will not be able to sand the finish as well, as the sticky balls are being swiped across the surface and not the sandpaper. You can remove the sticky balls with your fingers but after a while you can end up sanding your fingers. It is a good idea to keep a stir stick or a screwdriver around to remove the balls after swiping the surface a few times.

Green sandpaper, which is a new variety, tends to work better with latex as it does not clog as quickly. If you are not using this type though you should begin with a new piece of sandpaper when the clogs take over the current piece you are using. The problem of clogging the sandpaper can be avoided, for the most part, if you let the finish become completely dry before you start to sand.

The other thing you should know is when the sandpaper is worn out. When you are doing wet-sanding you will generally not get clogs since the water will carry away the slurry before the sandpaper becomes loaded with clogs. NOTE: if you are wet sanding and still getting the sticky balls you can add a couple of drops of liquid dishwashing soap to the water as this will probably keep the balls from forming. If they still occur the coat of the finish is not dry enough as you need to let the finish dry longer before you start to sand.

The best, and easiest, way to know when the sandpaper has worn out is run your finger lightly over the sandpaper you are currently using. Then run your finger over the new part of the sandpaper, such as the part that is wrapped around the sanding block. If there is a noticeable difference between the rough part and the new part then it is time to change the sandpaper.

More expensive sandpaper with abrasives such as silicon, carbide, and aluminum oxide will last longer than sandpaper with flint and garnet. They can be better in the long run as you do not need to change the sandpaper as often.

TIP: Do not throw away the old sandpaper after it has become word down. Worn down sandpaper is good to use on the last sand on a finished product as it will just take off a little bit of the finish. Many times on the last sand on the finish you do not want to use a newer piece as you can take off too much of the finish and it will not be as smooth.

Author: Jason Green