THE USE OF TOOTHPASTE AS A POLISHING AGENT FOR VIOLIN VARNISH

by William Ferguson

Violin Maker and Teacher Karl Roy once offered the following suggestion for an instrument CLEANING compound:

1/4 50% water, 50% alcohol.

1/4 Spirits of Camphor

1/4 Turpentine

1/4 Crest toothpaste in Non-Acidic Mineral Oil

If too dry, add more mineral oil. If too oily add more toothpaste.

With that precedent I decided to try toothpaste as a Varnish POLISHING agent. (Note: Polishing not Cleaning) I used Pepsodent Original (White) toothpaste as the polishing agent for the varnish of one instrument. It seemed to me to be as good or better looking as the polish produced by Pumice, Rottenstone and Mineral Oil.

I decided to look further into the potential of toothpaste as a polishing agent. A softwood board 36" x 3" x ½" was purchased at a Lowe's Store. It was sanded through 320 grit paper. Two coats of Clear Terpene Amber Varnish were applied to the front surface and each coat dried for one week in direct sunlight. I coated the back surface of the board with Watco Danish Natural Oil Finish. Subsequently, all other coats were applied to the front surface.

Then I applied a Glaze/Color coat of the same varnish mixed with Winsor-Newton Burnt Umber Artists' Oil Paint. After a week of drying in the sun I applied a second Glaze/Color coat of the same varnish mixed with Winsor-Newton Brown Madder Alizarin Artists' Oil Paint. After drying a week in the sun I applied a third Glaze/color coat of the same varnish and Winsor-Newton Brown Madder Alizarin Artists' Oil Paint. It dried for 6 days in the sun. Then a coat of Clear Terpene Amber Varnish was applied and dried for 9 days. A second Post Glaze/Color coat of Clear Terpene Amber Varnish was applied and allowed to dry for 26 days. A third coat of the Clear Amber Terpene Varnish was applied and allowed to dry for 22 days in direct sunlight.

I divided the now varnished and dried surface of the board into ten equal width sectors of about 91 mm each (about 3.6"). A Sharpie Ultra Fine Point pen was used to mark dividing lines between the sectors.

On the 94th day after the experiment was begun polishing of the varnish was begun. All sectors save the one being worked on were covered with Saran wrap. Rubberbands were placed over the Saran wrap directly over the Sharpie pen dividing lines at each side of the sector being polished. A different polishing compound/material was used to do the polishing for each sector. In applicable sectors of the varnished board, pieces of repeatedly washed and dried, essentially lint-free, baby diapers were used for the polishing cloths. A different clean, freshly washed and dried cloth was used for each sector. The polishing material was wiped off the just-polished sector with a slightly dampened Blue "Shop"-type paper towel and sometimes with a dampened Kleenex.

Approximately 150 "round-'n-round" strokes and 150 longitudinal strokes with the compound under test were used to polish each sector.

I feel sure that I physically "over-polished" each sector. I believe a nicer looking appearance of the varnish might have resulted from not quite such vigorous polishing.

POLISHING MATERIALS USED

The toothpastes used were:

Ultrabrite All In One, White. (Used in two separate sectors)

AquaFresh, white with green stripes.

Pepsodent, Original, White

Close Up, Original, Red

Colgate Regular Flavor, White.

To about a ½" to ¾" long strip of the toothpaste squeezed from its tube I added a few drops of tap water and proceeded with the polishing.

On one sector I did the polishing with 1000 grit MicroMesh followed by 1500 grit MicroMesh followed by 1800 grit MicroMesh. This proved to be much too coarse for polishing varnish. I made no further experiments with MicroMesh, being more interested in the toothpaste products as alternative polishing materials. But a Luthier at International Violin Co., Baltimore, told me that they commonly use MicroMesh nowadays in their shop to polish out varnishes.

One sector was left unpolished.

One sector was polished using Kremer Tripoli, Light pink, Catalog #99930 and Medicinal Grade Mineral Oil.

Another sector was polished with Kremer, Tripoli, Light pink, Catalog #99930 and Medicinal Grade Mineral Oil FOLLOWED by Brown Omega Rottenstone No. 598.

The varnished and polished board was sent to two separate professional experienced violin varnish examiners. Michael Darnton is a highly respected maker and instrument photographer in Chicago. Mr. Darnton has examined and photographed nearly a hundred of the Master Italian instruments including Stradivari and Guarneri del Gesu instruments. For about 9 years he wrote a column for the Guild of American Luthiers Journal.

Jeffrey Holmes is a maker and is Vice President of Shar Fine Instruments, Ann Arbor, MI. Mr. Holmes has had extensive experience in the acquisition, sale and restoration of fine bowed string instruments.

These two professionals were asked to evaluate the appearance of the polished varnish and to try to rank the quality of the varnish of each sector. The effect that the appearance of a violin varnish has on the individual looking at it is apparently quite subjective. Neither examiner identified the same sectors as the best tho' their descriptions were often similar. (To this inexperienced writer many of the sectors looked quite similar, excluding the sector subjected to MicroMesh.)

In my purely subjective opinion the grit sizes of commonly available toothpastes is comparable to the very finest grit sizes of MicroMesh. But I have not been able to find authoritative comparisons which interrelate the grit sizes of sand papers, MicroMesh and toothpastes. The American Dental Association uses their own grit size scale to measure the relative abrasivity of toothpastes. It is called the RDA (Radioactive Dentin Abrasion) Scale. This scale starts at 0 and is open ended. This method has been published in the Journal of Dental Research, Volume 61, No. 11, page 1236-1239. I have not been able to find out how their scale compares with the more familiar sand paper and MicroMesh abrasivity scales.

Conclusion: If you run out of pumice, rottenstone and diatomaceous earth and need to polish your violin varnish, give Toothpaste a try!

EVALUATIONS OF THE SECTORS BY Mr. MICHAEL DARNTON AND Mr. JEFFRY HOLMES

Michael Darnton Jeffrey Holmes
Sector 1 sanded; not polished MicroMesh 1000, 1500 and 1800 Sector 1 Dull finished; unpolished
Sector 2 Better than Average AquaFresh, white with green stripes. Sector 2 Nice moderate sheen. Shows pinholes in the varnish

Sector 3 Best overall

 

Kremer, Tripoli, Light pink, Catalog #99930 and Medicinal Grade Mineral Oil followed by Brown Omega Rottenstone No. 598. Sector 3 Similar to 2
Sector 4 Worst overall Untreated virgin varnish coats. Sector 4 Brighter; shows imprints from polishing rag? Slightly uneven. Brush strokes?
Sector 5 Below Average Ultrabrite All In One, White. Sector 5 Similar to 4 but surface texture better
Sector 6 Below Average Ultrabrite All In One, White. Sector 6 Duller; not as clear
Sector 7 Too glassy looking and too rough; maybe due to too fine a polishing compound? Colgate Regular Flavor, White. Sector 7 Very "bright"". Shows marks from polishing rag. Can still see brushstrokes.
Sector 8 Average Close Up Original, Red Sector 8 Similar to 7
Sector 9 Second Best, More shiny Mineral Kremer Tripoli Light pink. Catalog # 99930. Medicinal grade Oil. Sector 9 Similar to 8 but with slight haze
Sector 10 Third or fourth best but looking too glassy. Surface still good. Pepsodent Original, White. Sector 10 Also "bright." Surface texture "bumpy."
I like 3, 9 and 10 as best overall I like 5 and 8 best.
My least favorite for varied reasons: 4, 5, 6, and 8.
Michael Darnton Jeffrey Holmes