1970 Coupe Brake Booster Finish

[Chas]

Would like to know the original factory finish on the power brake booster. Was it yellow Zink?.......possibly black (flat, semi, or gloss)?......or just natural, untreated metal? Thanks in advance

[76eldo]

Chas,

I'd say natural untreated.  Certainly not black, and not gold cad.

Below is a photo of the booster on my 70 DeVille.  It's a 30,000 mile untouched car.

Hope this helps.

Brian

[Scot Minesinger]

If the brake booster was natural/untreated even a 7k miles CA car would be rust colored by now.  They were golden cad.  Don't have the authenticity manual handy but that might say.  Mine have all been finished in golden cad and no point deduct at GN.  Look at the hood hinges, those should match because those started life as golden cad.

[chrisntam]

I like the way this one looks......so much so I posted it twice......

[76eldo]

I just checked the authenticity manual and it does indicate a gold cad color.

I guess that fades.  Mine just looks like bare metal or bare metal with some mild zinc coating but I guess it started out as gold cad.

Brian

[Scot Minesinger]

Brian,

My hood hinges did the same thing

[Tom Hall 7485]

Scot, let's not bring the hood hinges into this.  The hood hinges were never iridescent gold.  They were a dull gray from the start, apparently Bonderite or something similar.  A color photo of one on a 1973 De Ville coming down the assembly line shows the dull gray.  GM Media photo C2207-0141.

[Scot Minesinger]

Tom,

The 1970 Cadillac had golden cad hood hinges, the finish remains fairly well complete on my 1970 SDV w/36k miles.  No question that the 1970 had golden cad hinges.  Check the authenticity manual.  The 1973 well I don't know, do not own one or researched it.

The only reason I brought it up is those products are same finish and may look the same.

[Tom Hall 7485]

Scot, are you suggesting that the hood hinges and brake booster cover have identical finishes?  The power brake unit was usually supplied by Delco-Moraine, wasn't it?  Did they use exactly the same processes as the company or companies that supplied the hinges? 

These treatments are a complicated topic.  They were not covered in depth in the Class 22 Authenticity Manual.  I am not a chemist or metallurgist, nor can I guarantee that all booster covers looked alike.  I probably spoke too broadly above. 

On the topic of the booster, what I think was done, and what Bill Anderson seemed to agree with four years ago, is that some booster covers apparently received two different layers, first a dull gray zinc something, which is more or less opaque and tends to remain many years later.  Scot, would you agree that some also got a second layer, a translucent something that allows some gray to show through?  What I believe to be a second layer is tricky to reproduce properly in restorations.  Some restorers seem to be applying an iridescent layer directly onto bare metal, and I'm not sure that's correct for the booster cover.  Also, some restorers are making a multi-colored iridescence for the booster cover, with the appearance at a distance of several feet not being either yellows (golds) or grays, but a combination of yellows, oranges, blues, greens and magenta.  So, when people call the color "gold", the question arises whether they are referring to these multi-colored platings/washes as well.

It would be good to find a factory color photo.  I suppose the brake booster might appear in photos of the body being lowered onto the chassis.

[Tom Hall 7485]

Here is a little desert archaeology which I think shows the two layers.  The appearance in my photo here is basically consistent with the photo that Mr. Rachlin posted above, except that this booster is on a derelict '72 Eldorado at a wrecking yard in Arizona, and it is much more deteriorated.  It also has more sunlight on it than we'd usually have if the hood were still on the car.  This additional sunlight may affect the appearance of the iridescent layer.  (The word "iridescence" is about major color changes based on lighting, angle and distance.  It is not to be confused with "translucent", which is about degree of transparency.)

At the outer edge of the booster, we can clearly see remnants of a gray something, which I am told is zinc.  I believe this is the first layer of plating.

Nearer the center of the cover, you can see some iridescence.  The predominant color of the iridescent layer is a faint yellow in this photo, but there are hints of some other colors, too.  It is perfectly natural that people call this iridescent layer "gold", but I think a better word to describe it is "iridescent".  This layer is not limited to yellows.  We can see a dot of turquoise in Mr. Rachlin's photo.  It is not only iridescent, but it may also be translucent, allowing some gray to show through.  This iridescent layer is probably on top of the gray layer.  The gray layer is opaque enough that it would probably conceal the iridescent layer if the gray were on top of it.

It is perfectly natural for people to think the gray layer is the bare sheet metal, or bare metal covered with dust or grime or oxidation, but it is not.  The bare metal here is now covered with rust.

It is also perfectly natural for people to assume that a low mileage car will look exactly the way it did forty or fifty years ago, and that is certainly our hope.  However, I can't be sure that the iridescent layer has held its colors perfectly over the years; some of that delicate layer may have oxidized into thin air over the years.

[Scot Minesinger]

Tom,

Yes the hood hinges and brake booster are supposed to be golden cad finish, possibly from different suppliers of course.  The actual finish process may vary slightly, but both would have this finish.  My low mileage 1970 SDV hood hinges retain much of the original finish and anyone examining them now would agree they are golden cad.  You went into the subject super deep, and I'm not into it that much.  You are well versed in this.  I cannot say for other years, as 1971 and newer certainly received many changes over the 1970 Cadillacs.

[chrisntam]

As President Bill Clinton so famously said, "It depends on what your definition of is is".



FWiW, my hood hinges also had remnants of the golden cad color until I painted them to clean them up.  They're now not judgeable, but they're a heck a lot better than they were.