Hugh,
I recently posted a similar request for info regarding salvaging and/or restoring Simplex "plastic" derailleurs on another bike forum and received responses ranging from Mother's "Back to Black" to lighter fluid, followed by a match, a hammer, a heavy boot, etc. Clearly a contentious issue. One member suggested the white bloom was caused by off-gassing as the Delrin gives up its volatile ingredients to atmospheric aging, but that's strictly a guess I would think. Vaseline petroleum jelly was suggested too, reputedly an old car detailer's trick. I decided I will try the Mother's product on my Criterium derailleurs though I admit the Jimi Hendrix approach was tempting.
Scott Gabriel
Cape Cod
US
> From: Hugh Thornton <hughwthornton@yahoo.co.uk>
\r?\n> Subject: [CR] Simplex "Plastic" Derailleurs - Questions For Material Scientists
\r?\n> To: "Classic Rendezvous" <classicrendezvous@bikelist.org>
\r?\n> Date: Monday, January 31, 2011, 9:02 AM
\r?\n> The plastic in Simplex derailleurs is
\r?\n> often referred to as Delrin (A Dupont acetal copolymer).
\r?\n> As far as I can remember back in the early 1960s, when they
\r?\n> first appeared, the publicity material referred to Delrin by
\r?\n> name and the name has been associated ever since. Does
\r?\n> anybody know whether Simplex continued to use Delrin or
\r?\n> whether they changed to another acetal or something else
\r?\n> altogether?
\r?\n>
\r?\n> Another thing I am interested in is the deterioration of
\r?\n> the finish and whether it is reversible. Occasionally
\r?\n> early models in white resin come on the market but very
\r?\n> yellowed. I have wondered whether that is through
\r?\n> absorption of oil. grease and dirt into the material such
\r?\n> that it is effectively permanent discoloration, or whether
\r?\n> it is on the surface and can be
\r?\n> removed.
\r?\n>
\r?\n> The common finish deterioration on the black plastic
\r?\n> moldings of later derailleurs is a blooming or whitening of
\r?\n> the finish. I assume this is caused by atmospheric
\r?\n> pollution or exposure to light. This does appear only to
\r?\n> be "skin deep" and it can be removed rather laboriously with
\r?\n> a mildly abrasive liquid such as car paint renovator. Does
\r?\n> anybody know if there is a better way, such as using some
\r?\n> not too noxious chemicals, that would make it easier to
\r?\n> renovate, especially in the nooks and crannies which are
\r?\n> hard to reach any other way?
\r?\n>
\r?\n> You might well ask why anybody would want to renovate a
\r?\n> Simplex derailleur when it is so much easier to throw it
\r?\n> away, but the better models such as the LJ 4000, referenced
\r?\n> recently by a listmember, are not so plentiful. The others
\r?\n> seem to be considered so plentiful and so disposable that a
\r?\n> world shortage of them could develop too.
\r?\n>
\r?\n> Hugh Thornton
\r?\n> Cheshire, England