Part 1: Preparing the Surface
The appearance of a finished surface depends on smoothness more than any other factor. Smoothness also plays a very important part in the durability and longevity of the coating. A rough surface will have small sharp edges and thin spots once the coating is applied to it (peaks). These spots (peaks) will tend to show premature “burn-through” or wearing due to insufficient coating thickness. It is therefore necessary to get the surface sanded smooth before any finish is applied.
Any wood that will have a finish applied to it must be sanded smooth. This is a process often greatly misunderstood. We hear people saying “I can’t sand my wood, too much will be lost”. This is a common misconception. Yes, you will lose some wood thickness, but it is absolutely necessary. No, you won’t lose too much. Maybe you will need to re-glue a couple of thin plugs, but that’s easy. It’s done all the time.
Sandpaper is sandpaper. All good boat and hardware stores carry decent brands. Three different grits are needed: 80 grit, 150 grit and 220 grit. Get plenty of each. Do not use and sandpaper finer than 220 grit or you risk loosing adhesion.
The Process: Bare Wood
This is a brief article, if our description does not make enough sense then do more research. There is a lot of information out there that goes into the basics, not to worry though the important part is all right here.
Step One: Sand the wood COMPLETELY smooth
Start with 80 grit paper. Use machines as much you can, and hand sand the tight spots. Sand and feel the results with your bare hand as you go, keep using the 80 grit until the wood is completely smooth with absolutely no high spots. Get rid of the dust with a small broom or an old paintbrush.
Step Two: Spots & Stains in the Wood
If your teak has black stains from weathering, now is the time to use teak cleaner. Use any good two-step teak cleaner to remove excess oil, stains, or discoloration from weathering. For other wood types, use a mild one-step wood cleaner as required. Follow the manufacturer’s instructions carefully and fully rinse to remove all residue. Allow the wood to dry completely for a minimum of 24 hours.
Step Three: Resume the Sanding Program
After sanding with 80 grit, regardless of cleaning, you now have smooth wood with small gouges in it from the 80 grit sandpaper. These must be smoothed out or they will show through the finish. This is what the 150 grit is for. Simply repeat the sanding process using the finer grit, sanding and feeling with your hand as you go. You will notice a big difference, and the start of a silky smoothness.
Step Four: The Finish Pass
You probably guessed this one- sand everything again with the 220 grit. This is to reduce the gouges left by the 150 grit.
Sounds like a lot of hard work? It really isn’t. In fact, it’s less work to get this step done right, compared to dealing with premature coating failure. Proper sanding is absolutely necessary. It’s not as hard as you think, and the results are very rewarding.
Previously Varnished or Finished Surfaces
One of the nice features of Bristol Finish is that it can be applied over existing finishes. If your existing finish is in decent condition this can save you a lot of labor. Of course, if that finish is badly deteriorated, it has to be removed. If the condition of your existing finish is good in some places and not in others is should be removed. Not doing this would result in variations in color and thickness.
Old Coating Removal
There are generally only two different coating removal situations that most boat owners face. The first is if teak oil has been used for years. In this case get plenty of teak cleaner and get to work. No coating will stick to teak oil. If oil was used a great deal it may take a couple of passes with the teak cleaner but it’s fast and easy.
The second is old thick failing varnish or some other built up finish. If in poor condition it will have to be removed The best way we’ve found to do this for varnish is with a heat gun and scrapers. This is the cleanest way we’ve found, and you avoid the toxic mess of paint remover. However, some modern finishes may require chemical removers.
In either case, after removing the old coating, you can then start the sanding program described above.
Existing Coatings in Good Condition
Areas that have an existing finish on them generally need only a fine sanding with 220 grit paper, to remove any oxidation on the surface, and also any minor roughness.
Sand by hand using even pressure. Make sure that the sandpaper is changed frequently. Use a red ScotchBrite™ pad on any corners and sharp edges to make sure that the coating is not removed all the way to the wood. Wipe away the dust frequently to make sure that all areas are evenly sanded and uniformly dull.
The Project Moves Along
After the sanding is done, clean away the dust and debris with brushes or brooms. Now you’re ready to look for any potential problem areas that need to be addressed. These are described in the next article, DIY Guidelines Part 2.
These steps may sound like a lot of work, but trust us- the old saying is completely true – proper and thorough preparation accounts for at least 90% of your success. These prep steps will pay off for many years to come, and make that beautiful finish stay that way for a long time!