OK, here's a long dissertation on restoring sewing machines, as I see it. Who am I to have an opinion on the subject when I am just a newbie to sewing machines? Well, I'm not a newbie to restoring metal and metalwork, I'm adept artistically...and I have always loved fine machinery of all kinds. SO....
I looked at all the cleaning methods both here and on ISMACS...which got into restoration, and I think that their methods are OK (if not harsh) for "museum restoration"-type approaches, but since there is no huge market value in "rare" sewing machines (do any sell for hundred of thousands of dollars?), and since there is no way around the "re-doing" of a rough machine to get it back to anything resembling it's original glory, and since re-doing is not "original" regardless of your approach....with an old machine that is rough, I'd much prefer a total makeover...complete finish-replacement, using modern finishing materials which are far superior in every way to old japanning and varnish.
In the case of my White VS-2, which has very nice metal but very little decal-ing left, I can sandblast the metal, spray it with synthetic coatings that will not scratch...like a car finish. Then I can duplicate the decal-ing from pictures of the same model (VS-2) and from "before" pictures...hand paint it...again with superior coatings. And finally, I can give multiple clear coats of a super hard polymer coating. I can then either buff and clear coat the shiny metal parts, or even re-chrome any thing that was chromed but rusted. If necessary, I could even get my buddy to machine any plates I need...from polished stainless if I wish. The machine would truly be better than original, and ready for twice the 125-odd years that it's lasted already....it could look better in 250 years, than it does today. I don't see that this approach takes a dang thing away from the machine at all. All of the essence of the machine...it's BUILD...it's beautiful mechanical workings...would remain intact. Only it's clothing would change, and that would be twice as good as original, yet look closer to original (ie: new) than if it had been "restored" using old techniques and to the degree that Glenn or Graham recommend, which leaves it's flaws still readily apparent. Call it's weathered, damaged facade "character" if you wish, but I'll take the machine's original character back any day, and start a whole new life together with it.
Don't care what Glenn or Graham think about this approach. I only agree with their approach in a situation where you have very significant original/new condition to begin with...THEN a museum restore makes sense (as in my 1923 66 Redeye...excellent original condition). If you have a machine whose condition doesn't really represent it's original glory, then "restoring" using original technique makes no real sense...it's still not "original" when you've messed with it (ie: when finished). And remaking it in a spectacular way with modern materials does no more harm to it than what they do in "restoring" it with old methods. You can always sandblast my spectacularly-remade machine and start over with original techniques...including remaking original decals if you wish. Truly, what does it matter it the machine's facade is half gone (or more) to begin with?
If you have a machine in ANY condition, and you want be true to maintaining it as original (ie: a TRUE museum piece), you cannot tinker with it except in the very minimalist fashion, so as to maintain it in it's current state and prevent further deterioration. Now THAT is the ONLY way to be true to preserving the actual original essence of the machine. You would never polish a rare coin, for example...or ANY museum piece, except in rare circumstance. Instead, you would simply arrest any deterioration, and place it in an environment which will protect it from further deterioration. So what Glenn and Graham do is not in reality any more "preservative" than what I would prefer to do in a restoration project. In my opinion, it is actually less so, since my methods would truly preserve the metal machine from deterioration much better than their use of original old materials and techniques. Theirs would simply preserve what's left of it's haggard looks.
That's the way I see it. I'd be much happier owning and USING a brand spankin' new 1880-90's White VS machine, than an ol' nag that I'm forever worrying about knocking off a piece of decal from her nose. I think I'd be honoring her and her makers more by a complete makeover than by a bath, a callus-sanding and corn-removal, any day, and I think they'd like it better if they were around, too, so long as I kept their same original motif. That part I'd faithfully reproduce by hand painted artwork...again, superior to decals.
That's the arduous and ardent makeover I have planned with ole Vicky Sue, too. (VS-2)
Now my Singin' Betty Red-Eyes, she'll be restored, since she's purty to begin with, and I'll just keep her as she is. I just hope she doesn't get jealous...
One last note...of course, by it's very nature, woodwork is ALWAYS a "restore" unless it's rotten, and then it's either get a new piece somewhere or build your own. That's because it has no underlying structure that is not directly related to it's outward appearance. That is not the case with a metal machine. It has both an inner and outer beauty. Therein lies the difference, the way I see it.