Re: [ATM] Dry Polishing?

["Jeremy Batterson" <jdbaterson@msn.com>]

Thanks. All three of these replies on dry polishing are highly interesting, and make good references. 
  ----- Original Message ----- 
  From: vorblesnak@peak.org<mailto:vorblesnak@peak.org> 
  To: atm@atmlist.net<mailto:atm@atmlist.net> 
  Sent: Saturday, January 08, 2005 6:01 PM
  Subject: [ATM] Dry Polishing .. Long


  For what it is worth, I have polished with paper and dry cerium.  The 
  only thing I could add is use no pressure, the weight of the glass is 
  enough.  I have used it to bring out a quick shine to look at the 
  curve.  I don't know how a finished mirror would look.  Here are a 
  couple of references from the past.

  A bit newer than Guy's reference.  From Scientific American, March 
  1949 and April 1950, by Albert Ingals.

  ELLISON'S condemnation of the dry paper, dry-rouge polishing lap 
  for telescope mirrors, contained in Amateur Telescope Making, 
  page 868, three years ago led Father M. Daisomont of Ostend, 
  Belgium, to send this department a printed polemic on the virtues of 
  that ill-reputed method. From his communication the two following 
  paragraphs are abstracted.

  "Reverend Ellison argues that paper laps cannot be deformed and 
  that they cause scratches. My mirrors show no scratches, and the 
  claim that the paper, because of its thickness, renders the 
  coincident curves of mirror and tool no longer the same radius by a 
  gross amount is erroneous. Calculation shows that the difference 
  thereby introduced is only 1/250,000-inch. The paper, pasted on the 
  glass tool, is brushed shaggy with bristles and fits after a few 
  strokes.

  "Polishing on pitch gives good results. Polishing on paper is at least 
  as good, but far simpler, cleaner, more manageable. Foucault made 
  wonderful mirrors with this, his method. It can produce real gems. 
  As for pitch, send it to the devil. It will then be in its element."

  In January, 1947, this department, seeking only the facts, published 
  a theoretical refutation of Ellison's claim that a sheet of paper throws 
  mirror and lap out of coincidence by the amounts he indicated. The 
  amount proved to be about the same as Father Daisomont had 
  stated. This department then invited him to furnish instructions for 
  the paper lap, together with a small sample of the paper he used. 
  These were received two years ago. He wrote, "I send the exact 
  description of how we prepare and use paper laps.

  "It is essential to use paper of excellent quality, pure, without 
  defects, unsized. We think well of duplicating paper 1/10-millimeter 
  thick. Make flour paste of soft consistency and strain it through fine 
  linen to avoid lumps. Clean the tool, rub on a light, uniform layer of 
  paste. Rinse paper in water, remove excess water between blotters, 
  lay it at once on the tool, and roll out excess liquid with hand or 
  roller. With a knife tip remove any hard grains in the paper.

  "When it is dry, cut around it with a razor blade, leaving a millimeter 
  to fold down. With an old toothbrush rub the paper to raise a light 
  down. With the hand put on a very little dry rouge, uniformly. 
  Remove surplus rouge with a toothbrush. The rouge layer should be 
  so light that the paper may easily be seen. If too thin during work, 
  add a little rouge."

  Copies of these instructions, with little samples of the Belgian paper, 
  which a New York paper manufacturer has called ordinary 
  mimeograph paper, have been sent from time to time in the past two 
  years to approximately 25 individuals and groups in the U. S. Most 
  of these declined to make the test. Some of them pointed out that in 
  Amateur Telescope Making Ellison had already settled the matter. 
  However, several did try the paper lap.

  In July, 1947, John M. Holeman, of Richland, Wash., reported: "The 
  paper lap is fast but gave a 'lemon-peel' finish, though not so bad a 
  one as a felt lap. Under test my mirror, polished four different times, 
  looked like blistered paint or ripple glass. The figure is easily 
  controlled with paper. Turned-down edge is not so bad as with the 
  soft pitch many use. The drag is great and a 10-minute spell of 
  polishing takes a lot out of one. After fine emery I polished in half an 
  hour. The lap is so fast that it is hard to figure with it.

  "Making the lap conform is the chief difficulty. Despite theory, the 
  paper's thickness or something does distort the curve and the edge 
  polished first. This can be handled by watching for it and buffing 
  down the lap with a suede leather wire brush-at the cost of as much 
  work as channeling a pitch lap."

  In March, 1948, J. J. Peabody and Dale Bufkin, of Elgin, Ill., 
  reported: 'We strongly suspect that 'Daisomont' is Albert Ingalls in 
  disguise! We battled as follows. With a six-inch f8 mirror we tried 
  eight grades of paper from .002- to .008-inch thick. We polished 180 
  hours on our machine at various speeds and under pressures 0 to 
  25 pounds, the lap eight inches in diameter. Also tried it three hours 
  by hand. Extreme caution is needed to avoid scratches. We tried 
  rouge, cerium, Barnesite. In every case, gross lemon peel showed 
  under test. On a pitch lap this vanished at once. Back on the paper 
  lap it reappeared. From theory, you admitted Ellison's error about 
  the fit of curves, but in practice he is right; they just don't fit. Radius 
  of outside zone came out 12 inches longer than central zone."

  W. A. Calder, professor at Agnes Scott College, Decatur, Ga., 
  reported: "Tried three times to polish, using mimeograph paper, 
  Scott tissue; rouge, Barnesite, dry; then with kerosene, again with 
  turpentine. Results inconclusive. I finally broke down and put the 
  mirror on a pitch lap, which did wonders in a few minutes."

  Rudolph Moulik, of Cicero, Ill., reported that the paper lap seemed 
  to be good when tested on two four-inch convex surfaces. However, 
  since convex shapes cannot be tested by the Foucault method, the 
  state of the surfaces could not have been studied. He attached the 
  paper with thin varnish and found that it was difficult to keep good 
  contact. He polished with Barnesite.

  Shown some of these reports, Father Daisomont replied in 
  December, 1947: "There is certainly something wrong with the work 
  of your American friends." His claims, many of them so emphatic 
  and extensive that there is not space to repeat them here (our 
  Daisomont file is now an inch thick), do indeed point toward the 
  conclusion that somewhere there is a large discrepancy; especially 
  in view of the fact that in one of his 11 letters he mentioned that he 
  had just polished and figured a six-inch f8.5 mirror in 10 hours on a 
  dry paper lap and that it showed the image of Saturn very well at 
  350 diameters.

  Therefore this department will pursue the discrepancy further. To 
  that end it has asked Father Daisomont for a little of his rouge and 
  enough paper for a lap, and will try to follow his instructions without 
  the slightest deviation. (It has also sent him Garnet Fines and told 
  him that after the* use, glass on glass, not only the large type 
  named by Ellison in ATM, page 79, but the text type of ATM could 
  be read through the mirror, dry, held seven inches below the eyes 
  and seven inches above the page; also that Barnesite, likewise 
  sent, would then polish the mirror on pitch, its sinful disposition 
  atoned for by speed and its fragrant aroma, in two hours.)



  IN March, 1949, this department described experimental attempts 
  several American amateur telescope makers to polish mirrors on 
  paper lap None turned out well. One worker r ported that these laps 
  gave heavy drag. The figure was easy to control, but co tact was 
  hard to maintain, and the surfaces produced were "lemon peel. 
  Another worked 180 hours, using a machine, but always obtained 
  lemon-peel surfaces. A third had contact troubles Yet Father M. 
  Daisomont of Ostend Belgium, the leading exponent of the paper 
  lap, stated without hedging that a six-inch mirror he polished with 
  rouge in 10 hours on a dry paper lap showed Saturn's rings well at 
  350 diameters. Regardless of long-standing dogma about the 
  inferiority of paper laps, this statement remains as a challenge to be 
  not merely disproved but investigated objectively.

  None of the experimenters followed Father Daisomont's working 
  directions. I tried to do this, and experienced no troubles with 
  contact, scratches or lap. The directions follow.

  Use common, rough, unfilled mimeograph paper of the kind 
  available at an commercial stationer. Cut out a rough circle an inch 
  or so larger than the tool. Dilute white library paste until sloppy and 
  smear it on the tool with the fingers, using a minimum covering 
  amount. Dip the paper in water, lay it for a moment between 
  blotters, and then place it on the tool. Smooth it out and leave it to 
  dry for a while with no mirror on top. When the paper is finally dry, 
  trim off nearly all the overhang with a razor blade.

  Dab a dry wad of tissue or rag in dry rouge and dab this on the lap. 
  Instead of attempting to spread it evenly, which may result in too 
  much rouge, dab it in evenly distributed blotches, which will spread 
  under work. If the lap remains red instead of pink after a little 
  polishing, with paper showing through white, make another lap. To 
  remove the old one soak it a minute and scratch it off with the 
  fingernails.

  An important source of satisfaction with a paper lap is the ease of 
  making another, so that there is no reluctance, as with a prized pitch 
  lap, to destroy it. It also permits resumption of interrupted polishing 
  with no preliminaries whatever. To those who do not enjoy the 
  fragrance of hot pitch, or who are repelled by lovely messes, or find 
  pitch possessed of seven devils, the paper lap is a lily-handed 
  escape.
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