Wood Surface Preparation with MIRKA® Abrasives

Wood Surface Preparation with MIRKA® Abrasives


An Early Twentieth-century Piano Bench Gets New Life


Published: 11/23/2014
By: Jerome Vernon
About the Author: Jerome Vernon is a software developer/project manager and an avid antiques enthusiast. When Jerome’s not busy creating business related software products for his clients he’s restoring antiques and writing articles for Restoration News.
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Wood Surface Preparation with MIRKA® Abrasives

An Early Twentieth-century Piano Bench Gets New Life



This is the third in a series of articles that focus on the utilization of abrasives and sanders particularly suited for restoration and refinishing of antiques and fine furnishings.

The first article, "MIRKA® CEROS - Innovative Sanders and Abrasives for Restoration and Refinishing" describes MIRKA's compact electric random orbital sanders, dust collector and accessory items. The article also briefly mentions MIRKA's 'Net' sanding concept and the advantages of dust-free sanding.

The second article, "Creating a Luxurious High-Gloss Finish" demonstrates how MIRKA® sanders, polishers and abrasives are utilized to achieve a beautiful high-gloss sheen while refinishing several mahogany panels.

With most refinishing projects there’s need for at least some hand sanding; reshaping and/or rebuilding worn edges, contours, fretwork, carvings or sanding within confined locations. This article will focus on surface preparation, primarily hand sanding procedures using an innovative product from MIRKA® Abrasives that makes the most delicate of sanding tasks simple and trouble free.



 Walnut Veneer Bench A few weeks ago while digging through storage I came across an early twentieth-century piano bench with twisted-rope turned legs.  The original multi-step finish on the walnut and walnut veneer over pine bench is dark-brown… almost black and totally dilapidated. This old bench will make a perfect specimen for demonstrating various aspects of surface preparation. 

The edges of the bench seat are particular rough with the corners completely worn away. I will need to fill and reshape these areas while preserving original dimensional characteristics. I will also need to sand by hand within the crevices of those twisted-rope turned legs.

Fortunately, MIRKA® Abrasives has the perfect product for sanding contoured surfaces and irregular, difficult-to-reach details by hand. With MIRKA’s Goldflex-Soft abrasives, surface preparation of contoured surfaces is a snap.  By combining the MIRKA’s CEROS tools with NET abrasives for dust-free machine sanding and, Goldflex-Soft for hand sanding, surface preparation of this piece will be relatively effortless.

"For me, these dark-stained walnut pieces can be a bit of a challenge to refinish. Walnut is an open-pore hardwood that varies from light-to-dark brown in color. It’s sometimes finished without staining; simply sealed with varnish, shellac, or other protective coating. Even without staining, the color of sealed walnut appears noticeably darkener then its natural, unsealed look. When applying stains to walnut it is easy to get overly-dark results so stains are often applied sparingly and in graduated steps."



Before starting let’s take a closer look at a few of the MIRKA abrasive products featured in this article...


Goldflex-Soft
Goldflex-Soft is perfect for fine sanding of wood and intermediate sanding of paint and topcoats. With its soft, flexible characteristics, Goldflex-Soft was developed for hand sanding profiled surfaces and irregular, difficult-to-reach details. The special stearate coating prevents clogging and the foam base is ‘grip friendly’ and applies pressure evenly to reduce the risk of producing ‘finger marks’. 

Goldflex-Soft is semi-open; it has an aluminum oxide grain with resin-over-resin bonding and a latex paper with PE-foam backing. Suitable for dry and wet sanding Goldflex-Soft is available in packages of 20 or 200 from P150 to P1000.



Polarshine 3 Polishing Compound
Polarshine 3 is an ultra-fine polishing compound, suitable for protecting the achieved high gloss finish on both paint and topcoat surfaces.

Polarshine 3 is excellent for buffing and sealing of surfaces and for hologram removal. It leaves a long lasting high gloss shine and it is ideal for demanding applications. Polarshine 3 contains NANO ANTISTATIC WAX (carnauba formulation) and suitable for both machine and hand application.









Process Steps

 Step 1 – Fill and Shape Voids

Following the removal of the old finish, the first step in surface preparation in to fill deep scratches, gouges and voids. This includes filling and reshaping damages corners or other structural components. With this project, the corners of the bench seat have been completely worn away. In recent years, wood-tone colored epoxy putty sticks have become a popular choice for wood repair. Epoxy putty is much more durable than traditional fill materials. It adheres well and can be easily shaped using knives, files and/or abrasives.  Several colors can be mixed together to achieve an acceptable color match for blending repairs with the target finish.

Shown left, several Mohawk Finishing Products Epoxy Putty Sticks are mixed and applied to the bench corners. Somewhat over-filled the putty is molded to the approximate contour of the routed edges. Dampening you fingers in water will help when forming the rough shape. The putty cures and is ready for machining within a few minutes.

For shaping of obvious overfilled areas, the cured putty is sanded using the 3 inch MIRKA CEROS with P120 Abranet. The lightweight 3 inch sander is easy to control and the Abranet abrasive cuts through cured epoxy with little effort. Being careful not to remove too much material, the epoxy is gradually cut away to achieve a more refined shape.

The epoxy putty is further refined to the exact contour of the surrounding woods using P150 MIRKA Goldflex-Soft.  Goldflex-Soft is an excellent choice because the latex paper with PE-foam backing conforms precisely to the surrounding contoured surfaces.  In addition, the PE-foam backing of Goldflex-Soft reduces the risk of producing depressions (finger marks) along the surface.

(Note: epoxy putty sticks work great for repairing oversized and/or striped screw holes. Shown left, a small amount of neutral colored epoxy putty is mixed and packed into several striped screw-holes used for attaching the hinges on the bottom of the seat. A toothpick or other round wooden stock material is used to pack the putty and, for creating a small screw-hole impression in the center of the packed hole.)


 Step 2 – Sanding

In this step, I will sand all surfaces, beginning with P150, P240 and ending with P280 and P320 on the flat surfaces. Some argue against sanding in general but I have found the sanding step to be important for several reasons. Sanding levels the fillers applied to deep voids and removes minor surface scratches. It also removes unwanted remnants left behind after finish removal as well as various discolorations while achieving uniformity in both overall color and the texture of the wood.

The larger flat surface areas are sanded using the 6 inch MIRKA CEROS with Abranet abrasive. Starting with P150, the filled areas are leveled and other imperfections are beginning to disappear. The majority of sanding is done in the center areas while sanding along the edges is substantially minimized. While sanding along the edges it’s important to apply minimal pressure while keeping the sander flat (not tilted towards edge) and in constant motion. More severe surface imperfection will remain in view after sanding with the coarser grits and will completely disappear only upon sanding with the finest grit. Removing the least amount of material possible while achieving a uniform surface that’s ready for finishing is the end-goal of sanding.

(Note: for this project the final grit of Abranet abrasives was P320 on flat surfaces.  Although walnut is an open pour wood, for this project, grain filler will not be applied. A final scuff sanding with P320 slightly reduces grain rift thus aiding in adherence to maximum topcoat thickness specifications while achieving a level finish. Depending upon the actual wood species, characteristics and finish schedule this may not be plausible for all situations.)

After sanding the larger flat surfaces, focus shifts to those hard-to-reach areas. Shown left, MIRKA Goldflex-Soft is available in 11 grit ranges, from P150 to P1000 and is available from numerous distributers in 20 or 200 piece packaging. MIRKA Goldflex-Soft is robust and far outlasts traditional abrasives.

(For surface preparation, I have found the lower grit ranges indispensable so, the 200 piece container is the best value and most convenient.)

To get into the crevices of the twisted-rope turned legs I wrapped the Goldflex-Soft around a short piece of 3/8 dowel stock. This made the task simple and quick. The Goldflex-Soft abrasive material conformed uniformly to the curved surfaces and the material was rotated on the dowel as needed during the process. Three sheets of Goldflex-Soft P150, P180 and P240 were used to sand all four legs on the bench.

Shown left, a shape cabinet scraper is used to cut away remaining debris and to prepare surfaces adjacent to joints and other impossible-to-reach locations. Cabinet scrapers are the tool of choice for many woodworking and refinishing tasks however, require a bit of practice with respect to proper usage and sharpening.

The final picture in this step shows the bench with surface preparation completed ready for finishing.


Step 3 – Bleach, Dye and Stain

After surface preparation, it was obvious that the veneer on the seat was considerably darker than the other woods of the bench. This color difference would show though when finished. A wood bleaching treatment was applied to bring the color into closer uniformity and lighten the piece overall. An oxalic acid (wood bleach) treatment was applied to the seat twice and then once to the remainder of the bench. After the bleaching treatments all woods were neutralized in a borax rinse and then clear water and left to dry ~24 hours.

A yellow dye stain was spray applied and the bench was sealed using Mohawk Finishing Product vinyl sealer. After sealing, all surfaces were lightly sanded (scuff sanded); sanded just enough to remove the raised wood fibers. The flat surfaces were sanded using a 6 inch MIRKA CEROS with P320 Abranet. The routed edges were sanded using P320 MIRKA Goldflex-Soft.

Next, Mohawk Finishing Product vandyke brown Finisher Glaze was applied. The glazing stain was applied first by rag then a glazing/graining brush was used to sweep the stain over the surface; creating highlights and shading until the desired look was achieved.

After staining the twisted-rope turned legs, the outside edges of the legs were gently wiped using a naphtha dampened rag wrapped around a felt block. This (tipping procedure) removed a bit of the glazing stain thus providing an interesting sense of contrast and old-world charm to the overall look of the piece.

Notice the bench has ample color and that the natural grain pattern is accentuated and fully visible. We are now ready to apply the topcoat.




Step 4 – Apply Topcoat

Mohawk Buffcote Lacquer is a great choice for antiques. It contains waxes with a light amber color and provides a vintage hand-rubbed appearance straight from the can. Four coats of satin (40 Sheen) lacquer are spray applied. The first two full coats are applied unreduced. The third and fourth coats are applied reduced by 25% (3:1) using lacquer reducer. The third and fourth coats also included a retarder to aid in flow out of material.

After the second coat dried (~4 hours), the bench was sanded lightly using P320 ABRANET. After the third coat dried (~4 hours), the bench was sanded lightly using P400 ABRANET. During both sanding procedures a 5mm interface pad was used and the MIRKA® CEROS set to a modest speed. Also, during the sanding operation the wood and abrasive is frequently cleaned. ABRANET abrasives can be easily cleaned using a small brush then re-used on future projects. After sanding and before applying a subsequent coat of lacquer, the bench was thoroughly cleaned by wiping with a lint-free rag dampened in Mohawk SILICONE WASH.

After the first sanding/cleaning procedure the top surface (bench seat) is inspected for unfiled gouges. If left unfiled these small voids would show up as imperfections in the final finish. Shown left, a small unfiled gouge is being filled (over-filled) with lacquer. The gouge was filled by applying one drop of lacquer directly into the void using a small fine-tip artist brush.


Step 5 – Rubout and Polish

In this step, I will briefly demonstrate rubout and polishing of the topcoat for achieving an exceedingly smooth surface over the Satin (40 Sheen) lacquer. The final process described here demonstrates MIRKA Polarshine 3 ultra-fine polishing compound containing a NANO ANTISTATIC WAX (carnauba formulation). For more detailed information regarding the rubout and polishing process please visit the companion article: Creating a Luxurious High-Gloss Finish

The rubout procedure corrects minor finish defects and establishes a level surface above the (rifts) of the wood grain. We will begin by sanding with MIRKA® MICROSTAR which has a special stearate layer and a smooth film backing. A 5mm interface pad is used with the MIRKA® CEROS tool set to its lowest speed. Sanding begins with P800 MICROSTAR and ends with P1000 MICROSTAR. At this point, dry sanding stops and wet sanding using MIRKA® ABRALON begins.  ABRALON is used here for wet sanding to a gloss surface prior to polishing. A small amount of a wet lubricating agent, Mohawk WOOL-LUBE, is applied to both ABRALON pad and surface. For this project sanding (sheen adjustment) began with P1000 and ended with P2000 ABRALON while cleaning the surface before advancing to the next grit.

After rubout and sheen adjustment, the bench seat is polished using the MIRKA® 77mm (3 inch) Rotary Polisher and POLARSHINE liquid polishing compounds. The polisher will be run at low speeds so, the pressure regulator is set to 60 PSI. Before advancing to the subsequently finer polish the surface is cleaned by wiping with the wood grain using a clean, pre-dampened micro fiber towel.

Polishing begins with POLARSHINE 10 medium coarse polishing compound using a twisted wool pad. Two full passes are adequate for removal of P1500 and finer scratch patterns. After cleaning, polishing continues with POLARSHINE VF5 fine polishing compound using a black foam pad. Several passes are adequate for removal of P2500 and finer scratch patterns. The final procedure is to polish and protect the bench seat by applying Polarshine 3 ultra-fine polishing compound using a black foam pad.

(Note: At the microscopic level coatings such as lacquer and shellac are porous. Water and other contaminants can diffuse through coatings causing contamination issues such as moisture blooming. Polarshine 3 combines an ultra-fine abrasive with antistatic NANOWAX (emulsion of< 100 nm droplet size carnauba and antistatic surfactant) which provides excellent hydrophobic protection while inhibiting accumulations of dust and contaminates.)



Conclusion
After sanding and lighting the woods with an oxalic acid bleaching treatment the beautiful grain pattern of the once dark-and-dreary piano bench has emerged and is now visibly accentuated. Rebuilding and reshaping edges worn completely away and, surface preparation using the MIRKA® CEROS tool with Abranet and Goldflex-Soft for hand sanding was the key to achieving an impressive finish.

I was particularly impressed with the performance of MIRKA® Goldflex-Soft abrasives for hand sanding. Goldflex-Soft made a once argues task easy. Traditional sheet abrasives simply cannot compare to the ease-of-use, robust nature and surface conformity of Goldflex-Soft.

The final rubout and polishing of the Mohawk Buffcote lacquer in a satin sheen provided a semi-reflective surface along with a soft amber glow. By applying MIRKA® Polarshine 3 ultra-fine polishing compound with antistatic NANOWAX as the final step, the finished surface actually repels dust while simultaneously providing a durable layer of protection from liquids and other contaminants.

(As I was applying the finishing touches to the bench, my lovely daughter happened by for an afternoon visit.  During our visit she commented on how nice the bench turned out while hinting how beautiful it would look in her house. Needless to say, this old piano bench now graces the foyer of my daughter’s home.  I have no doubt that it will proudly remain in her young family for future generations to come.)

In an upcoming related article I will demonstrate the usage of MIRKA® Abrasives products and how they are utilized during the restoration of an original but tattered existing finish.


MIRKA® Distributors
MIRKA® sanders and abrasives are available world-wide through an extensive network of distributors. Here is a link that has a listing of distributors within USA: [MIRKA® CEROS USA Distributors].

Disclosures
Restoration News accepted no monitory award, support or payment from MIRKA® Abrasives for the development and publication of this article and its content. The content, usage guidance and, general opinions regarding all products mentioned here are the sole opinions of the Restoration News staff; as determined by their independent interpretation, analysis and testing.  In addition, Restoration News assumes sole responsibility for all content contained in this article as defined by Restoration News limitation of liability and website disclaimers.


Materials Warning Statement
This is not an OSHA/NOSHA recognized warning. One or more of the products described here is flammable. To prevent death or serious injury, proper precautions must be observed. Refer to product material safety sheet for detailed information. Flammable liquid and vapor, keep away from heat/sparks/open flames/hot surfaces. Keep container tightly closed.
One or more of the products described here causes lung, eye, skin, nose and, throat irritation. To prevent death or serious injury, proper precautions must be observed. Refer to product material safety sheet for detailed information. Harmful or fatal if swallowed, may be harmful if absorbed through the skin, vapor harmful. A NIOSH-approved air-purifying respirator with the appropriate cartridge may be appropriate under certain circumstances


For material safety data sheets, product data sheets and, addition instructional guides; visit our Downloads Page: [Click Here]






References
  
MIRKA Woodworking Website (USA)
   Explains MIRKA Sanders and Abrasives for Woodworking
  
MIRKA Website (North America)
   Sanders, Polishers and Abrasives
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