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Questions: Power Buffer For Finish

Questions: Power Buffer For Finish

by Charles Fox

Originally published in American Lutherie #79, 2004 and Big Red Book of American Lutherie Volume Seven, 2015

 

See also,
Questions: Post Buffing Finish Scratches by Brian Boedigheimer

 

Mario from cyberspace asks:

I use a power buffer to rub out my finish. It looks perfect to me at the time, but sometimes in other light I can see little tiny scratches that I’ve missed. Any advice?


Charles Fox of Portland, Oregon
responds:

That reminds me of when I brought instruments to my first music trade show a few decades ago. Under the unforgiving glare of the convention center’s halogen lights I was appalled to see that the guitars, which I thought were perfectly finished, were in fact covered with tiny scratches that hadn’t been visible to me under either tungsten, fluorescent, or natural sun light. Now I do all of my finish work beneath halogen work lights. You can get an excellent ceiling shop light with double halogen lamps (part # 73995) from www.Rockler.com for $34.99. ◆

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Letter: Clarification of DVD review in AL#97

Letter: Clarification of DVD review in AL#97

by Ronald Louis Fernández

Originally published in American Lutherie #99, 2009



Greetings,

I thank Tom Harper for his review of my DVD, French Polishing for Guitarmakers 2.0 in AL#97. I wish to make a few clarifications.

My family’s Spanish guitar business in the 1960s never involved Manuel Rodríguez. Rather, we had dealings with Miguel Rodríguez of Cordoba as well as Manuel de la Chica (Granada), Arcángel Fernández, Marcelino Barbero, Felix Manzanero, Hernández y Aguado, Juan Alvarez, and José Ramírez III. My article “Miguel Rodríguez: Some Notes on his Family Tree and Correcting the Historical Record” in AL#68 (Winter 2001) tells about the Miguel Rodríguez family and mentions my dealing with them. In a footnote of that article, I specifically mention the difference between Miguel Rodríguez of Cordoba and Manuel Rodríguez of Madrid.

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Questions: Post Buffing Finish Scratches

Questions: Post Buffing Finish Scratches

by Brian Boedigheimer

Originally published in American Lutherie #86, 2006

 

See also,
Questions: Power Buffer For Finish by Charles Fox

 

Brian Boedigheimer of River Falls, WI responds to Mario’s question in AL#79 regarding what to do about tiny scratches in finish noticed after buffing:

Charles Fox responded earlier to discuss lighting and I certainly agree lighting is key in so much of the work we do. Another thing to consider is the grading system of the abrasives one chooses to level the finish. There are three systems: CAMI, which is the U.S. standard grading system; FEPA, the European standard; and Micron grading. FEPA P800 is equivalent to CAMI 400. The P indicates the FEPA grading system, which is important because the grit particles are more uniform than in the CAMI system. Therefore there’s less chance of a stray large particle causing a scratch that we won’t see until buffing. So P800 gives you the cutting action of a 400 grit without the stray (larger) particles of the CAMI rating. Micron has the tightest tolerances for particle size, and if you have access to Micron-graded paper, that’s even better than FEPA. The equivalent Micron grade would be around 25 or 20. I recommend the FEPA grading system for abrading coatings until you’re into compounds; then you’re dealing with Micron.

When sanding to level finish, the coarsest grit I would use is P400 grit, but typically I start with P600 or higher. I used to go through the process level-sanding with 320, 400, 600, and so on. The problem is, if you miss a 320-grit scratch working through the higher grits, you won’t know it until you buff out the guitar, and only in the right light will you see it.

Now when I level-sand my finish before the final coats, I use P800 and spend just a little extra time with that one grit. It really doesn’t take me much longer, and I know those tiny scratches won’t suddenly appear. Then I spray the final two or three coats. Once that’s cured, I only have one grit of wet sanding to do before buffing. At that point I choose P1200.

Don’t think that because each layer of nitrocellulose lacquer melts into the previous one, you won’t have stray 320 scratches show up. Even with that specific bond, a stray particle scratch from 320-grit CAMI-graded paper will show up when buffed out. I’ve experienced it. ◆

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Seedlac

Seedlac

by Nicholas Von Robison

Originally published in Guild of American Luthiers Data Sheet #150, 1980 and Big Red Book of American Lutherie Volume One, 2000



Seedlac resin, when combined with alcohol, gives a magnificent spirit varnish suitable for spraying or French polishing with qualities far superior to its better known cousin shellac. It’s more transparent, faster drying, harder, and more resistant to scuffing and moisture. The latter quality is of particular value as sweaty hands can play havoc on a shellac-based finish on a musical instrument. With all this going for it, it is not well known or used by luthiers to a great extent. The primary reason is that the major paint and varnish manufacturers buy most of the crop for their own needs, leaving little for the small-scale importers.

About 60% of the resin is collected from an area between Calcutta and Central India with lesser amounts coming from Myanmar, Thailand, and Laos. There is a distinct difference in the resin color from different areas. The lac west of Calcutta is yellow or orange, east and south of Calcutta it is red, a pale red in Assam, and a dark red in Thailand. The resin comes from various indigenous trees, primarily kusam (Scheichera trijuga) which has the best color (pale yellow) and quality, but others such as pala (Wrightia tomentosa), ber (Berrya amomilla), and ghont (Bursera serrata). Two crops occur each year, summer and winter, and they revolve around the life cycle of a scale-like insect (Laccifer lacca) which infests the host trees. This small (about the size of an apple seed) red critter was cultivated as early as 80 A.D. for the purplish dye it contains. But not until 1580, in the records of Akbar the Great, do we find any mention of seedlac resin for varnish making.

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Honest Ron’s Lacquer Finishing Technique

Honest Ron’s Lacquer Finishing Technique

by Ron Lira

Originally published in Guild of American Luthiers Data Sheets #262, 1983 and Big Red Book of American Lutherie, Volume One, 2000


Tools and Materials:
High quality spray gun — Binks 69
Respirator and rubber gloves
1/2 h.p. or larger compressor
2 water traps in air line — Amflo 1060
Air regulator for 40 lbs.–50 lbs. static — Binks
Hot plate with water tub
Clean place to spray
Air or electric buffer and pads
     Rodac 717 and Schlegel 875C pads
120-, 220-, 320-, 600-grit sandpaper
     3M Tri-M-ite Fre-cut and wet or dry
Behlen Pore-o-Pac paste wood filler
Sherwin Williams T75C40 Finish lacquer
Sherwin Williams T67F3 Vinyl sanding sealer
Sherwin Williams R7K120 Thinner
Sherwin Williams R7K27 Retarder
Sherwin Williams D1T271 Rubbing compound
Sherwin Williams D1T13 Polishing compound
3-M-05990 Imperial Hand glaze

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This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page.

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