Wood Sanding for a "Green" Finish

If you're hopping on board the "Green Finishing" train, you need to consider how to move from solvent-based coatings into water-based finishing. The average final sanding grit for solvent-based finishes ranges between 150-220 grit. When using water-based finishes, the final sanding grit usually runs between 220-280 grit. Moving to a higher abrasive grit for water-based finishes allows for a higher polish of the wood to reduce fiber raise and minimize stain blotching of the wood.

Softer species of wood will stain best when up to 280 grit sanding abrasives are used. Harder, tight grained species of wood may only need the 220 grit as a final sand. To be successful in water-based finishing, you need to rethink the process from start to finish. This surface preparation is your first step.

If you would like to try some sample sanding products in a finer grit for water-based finishing, please visit our website at www.abrasiveresource.com or give us a call at 800-814-7358!

Surface Speeds for Metal Finishing

The effect of surface speed when grinding and finishing metals is addressed in the "Metal Finishing Guidebook", published by Elsevier. They ask us to think of each individual abrasive particle on the abrasive belt as a single point cutting tool. The speed of the belt or number of times a minute each particle contacts the work in a given time frame, will determine the rate of removal and the working life of the individual particle. An increase in the surface speed will cause the pressure to be applied to many more particles in a given time frame and will reduce the penetration of a given particle into the workpiece. When this speed reaches beyond a critical point, rapid dulling of the abrasive grain takes place, the rate of cut decreases, and excess heat is generated.

To resharpen or restore the cutting capacity of the abrasive, added pressure must be exerted to cause fracture of the grain. This added pressure will generate added heat and soon, burning will result in removal of the belt. Conversely, as speeds are slowed, more pressure is exerted on each grain, causing the grain to resharpen with less heat generation. To understand this more fully, the Metal Finishing Guidebook refers us to the following table, where suggested speeds, abrasive, contact wheel, grit size, lubricant and operation have been compiled into a quick reference chart: Suggested Surface Speed and Abrasives for Various Metals.
If you have any questions regarding abrasive belts, please give Abrasive Resource a call at 800-814-7358 or visit us online at www.abrasiveresource.com.

Revive Your Furniture's Finish

If the finish on your furniture appears dull and dry, but is otherwise intact, you can revive it with a simple cleaning and a coat of wax.

Start by wiping the finish thoroughly with a clean rag dampened with naphtha. Naphtha is a fast drying solvent that is often used as a lubricant for rubbing out hardened shellac finishes and can improve an older shellac coating with a simple rub down. One of the most popular is VM&P Naphtha, which should be available at the big box home improvement stores as well as hardware stores and paint stores. This step removes any oil-soluble grime.

Then, switch to a detergent to remove water-soluble dirt. One squirt of Dawn
brand dishwashing liquid mixed into a pint of warm water. Use a slightly dampened cloth, not one that is dripping wet!

Next, lightly dry sand the finish with a 400 grit sandpaper and follow up with a 600 grit. The goal here is to remove only the very top layer of finish, but not to sand all the way through to the wood.

Wipe off the sanding dust with a rag dampened with the naphtha and then use a natural or dark-colored paste wax (depending on the color of your wood) to bring the luster back up.

"Buffing out a Finish"

Whether you are buffing out a car, a floor, some metal parts, a countertop or even the finish on a guitar...the verb "buff" derives from the obsolete English word buffe, from the French word for buffalo.

When buffalo were abundant in the 19th century, buffalo hide was used for polishing metal to a high gloss. Soon, any sort of soft leather used for polishing was coined as a "buff", which then inspired the verb "to buff".

Sandpaper Grits

Sandpaper grit size refers to the size of the particles of abrading materials embedded in the sandpaper. There are a number of different standards that have been established for grit size. These standards establish not only the average grit size, but also the allowable variation from the average. The two most common are the United States CAMI (Coated Abrasive Manufacturers Institute, now part of the Unified Abrasives Manufacturers' Association) and the European FEPA (Federation of European Producers of Abrasives) "P" grade. The FEPA system is the same as the ISO 6344 standard. An additional measuring system used in sandpaper grits is micron grade (generally used for very fine grits). Also, cheaper sandpapers sometimes are sold with nomenclature such as "Coarse", "Medium" and "Fine", but it is never clear to what standards these names refer.

FEPA Grading: The majority of coated abrasives manufactured today use the FEPA standard (Federation of European Producers of Abrasives), otherwise known in the industry as “P” grading. Abrasives in the P scale are graded to higher tolerances than CAMI graded abrasives.

CAMI Grading: This grading standard is used exclusively by US manufacturers of coated abrasives, and is overseen by the Coated Abrasive Manufacturer’s Institute and the American National Standards Institute (ANSI). The CAMI-scale tolerates a wider range of grain sizes within the definition of the grit.

Micron Grading: This refers to an abrasive particle’s actual diameter in micrometers, rather than the total number of abrasive grains that can pass through a linear inch in a screen or mesh (as the FEPA and CAMI grading system use). Micron grading has the tightest tolerances for grain size and in abrasives are typically used only in fine grits, when a stray scratch from an outsized grain would make a substantial difference to the finish.

If you have additional questions about sandpaper grits and how they compare to one another, please give Abrasive Resource a call at 800-814-7358 and be sure to download our grit comparsion chart at abrasiveresource.com

Abrasive Resource is your source for the finest abrasive products!

Surface Prep on Metallic Paint Cars

In the January 2010 issue of Bodyshop Business, contributor Nathan Tarr writes on how to "Conquer Metallic Colors". Nate is both Sikkens certified and PPG certified and has been working as a painter for the past five years. Here's an excerpt pertaining to the importance of proper sanding...

Surface Prep: As with all facets of working with tough metallic paint jobs, your surface prep needs to be extra thorough. Any errant sanding or scuffing scratch is no big deal on normal paint jobs, but it can be magnified 10 times when working on a champagne color or anything Honda has named Satin Silver Metallic. Being a little less aggressive will serve you well during your paint job. Consider bringing the sanding grits you use down a notch, and be extra careful with any scuff sanding. There’s no real need to be pressing down on a scuffing pad like a gorilla. With a carefully prepped and clean panel, the risk of any cringe-worthy metallic tracking will be minimized.

To read the entire article visit the Bodyshop Business website.

Sanding Hardwood Floors

Preparing to Refinish a Hardwood Floor:

1. Inspect the floor carefully. Most oak floorings are 3/4" thick and can be sanded a number of times.  Remove a floor register if possible, and measure the thickness of your flooring. If it is thinner than 3/4" you should consult a professional floor refinisher. Thinner floors must be refinished with the utmost skill and caution to avoid sanding through to the subfloor.

2. Try to remove the shoe molding, if applicable, so that you can sand all the way to the wall.

3. Inspect the floor carefully--tighten any loose boards and pull out or counter-sink any protruding nails or staples. Sanding exposed nails can produce sparks, which creates a fire hazard in the sander!

4. Check fuse supply as sander may overload the circuit in an older building.

5. Provide adequate ventilation.

6. Cover arches or doorways with a dropcloth or plastic covering. Stuff towels under bottoms of doors and cover all air vents.

7. Sweep the floor clean immediately before sanding.

Renting a Sander & Purchasing Sandpaper:

1. When you rent a sander, be sure you get the manufacturer's instruction manual and some hints and/or a demonstration from the store where you rented it.  Be sure you also have any attachments, special wrenches and dust bags needed. Floor sanders are powerful machines and if not used properly can quickly gouge your floor beyond repair.

2. Purchase a dust mask and ear plugs if you don't already have them.

3. Purchase the appropriate sanding discs, sheets or belts to go with your sander(s). An average room will require 10 sheets, discs or belts of each grade. If you will be sanding more than one room, it is worth it to call ahead of time and order from a sandpaper supplier like www.abrasiveresource.com rather than the rental store. If you are only sanding one room, the quantity of paper needed is small enough to just buy the sanding supplies right from the rental store.

4. If you are refinishing an old floor and need to remove paint or sand cupped boards, start with a coarse grit like 16 or 20 grit and then move onto the 36 and 50 grit paper. If you are sanding an older floor that is in good shape, you may start with a 36 grit to just remove shellac or varnish. If you are sanding a new floor, simply begin with the 50 grit paper.

5. Your next sanding will use an 80 grit  and the final sand can be a 100 or finer grit. 

6. For a professional looking finish, use 2 different types of sanders--a large sander for the main area of the space and a smaller edge sander to get up close to the walls.

Sanding Hardwood Floors:

1. It's a good idea to practice first with a piece of your fine grit sandpaper just to get the "feel" of how your sander works. That way, as you are getting used to the process you are less apt to make a heavy gouge in the wood. When you feel comfortable, switch to the coarse grit to get started.

2. Your first process in sanding uses the coarse grit sandpaper. You are removing any previous stain, finish and discoloration as well as leveling the floor to a smooth surface. If the floor has warped boards or ridges where two boards come together, you may need to sand diagonally across the floor until smooth and then sand with the same grit again with the grain of the wood to get the sanding marks left by the diagonal sanding out.

3. Be prepared to change your paper regularly. The heat from the friction of sanding melts any old finish and this clogs up the sandpaper, making it ineffective. If you start to notice that the sanding rate is dropping, your sandpaper is probably clogged or worn out. Stop sanding and change your paper. If you continue operating with a worn out or clogged sanding paper you will eventually burn or damage your floor!

4. Follow the instructions for your particular sander. Let the sander pull you forward at a slow, steady speed. You can sand both forward and backward, but always keep the sander in motion.

5. Sand two-thirds of the floor in one direction(with the grain), then turn 180' around and sand the final third of the room with the grain. Overlap your back-and-forth passes to be sure you are sanding all areas thoroughly and to assure an even, blended finish with no sanding marks. Go forward and then return over the same area as you go backward. Move sideways in 3" or 4" increments to overlap each pass. Do not attempt to remove 100% of the old finish during this operation. Small residual amounts will be removed during your subsequent passes.

6. It's a good idea to vacuum the floor between each grit so that you aren't sanding random pieces of the coarse grit paper that may have shelled off during sanding into the floor with your next finer grit.

7. After you have done the main part of the floor with the rougher paper, use either a rented edge sander or an electric vibrating sander to sand where the floor meets the wall and in any other areas missed by the big sander using your next grit in the sequence.

8. After your 50 grit sanding, fill all dents, gouges and cracks still remaining with a commercial wood filler that is easy to sand and will accept a stain. If you have large areas that need filling, you will have to do this process twice, as the filler will shrink a bit when it dries. Allow extra time here for the filler to dry...

9. Now use your 80 grit paper to smooth the latex floor filler and remove the scratches produced by the 50 grit sandpaper. 

10. Hand sand all the areas your electric sanders could not reach--inside corners, around door casings and jambs, up to cabinet kick plates, etc.

11. Time for your final sand using a 100 or 120 grit sandpaper.

12. Vacuum the floor well--to be extra sure all the dust is up you may want to tack the floor clean with a paint thinner soaked towel wrapped around a push broom or swiffer. Now you are ready to finish!

If you have questions or comments, please call Abrasive Resource at 800-814-7358. We supply floor sanding supplies from our warehouse in NY and can drop ship to addresses anywhere in the United States.