Whitening Old Knobs

[1929Chrysler]

Any ideas on how to whiten Knobs that have turned yellow over the years? Presumably it is plastic from the 60's. Thank you in advance.

[Guest Jim_Edwards]

Any ideas on how to whiten Knobs that have turned yellow over the years? Presumably it is plastic from the 60's. Thank you in advance.

Most plastic knobs of the '60s were never "white" most were more of an Ivory. Actually now that I think about it, even the knobs or associated plastic trim around them in the '40s through the '60s were more an Ivory.

Jim

[Tom Martinez]

Try polishing them with laquer thinner, I've used this method on old Volkswagen and Porsche knobs which tend to crack and yellow with age. Test a small area first to guage the possible results. becareful because the thinner will create a melting action, this is what removes any crazing too. I've had good luck mounting the knob on a drill motor and applying the laquer thinner with a soft cloth to acheive the polishing action. I too have never seen truly white knobs on any car, they are usualy a yellowish ivory that become more yellow with age.

Regards and Blue Skies, Tom

[1957buickjim]

My suggestion would be to compound them just like you would paint. Start with a heavy rubbing compound then work on progressively finer compounds until you use a swirl remover type of compound. The lacquer approach sounds like if you mess up, your knob is forever marred or messed up, since the lacquer thinner will melt the plastic. As a back up, you could always fill the cracks with a polyester glazing compound and sand, finish and paint the knobs the original color (you can probably buy model car paints at a hobby shop and mix to the right color). In reality, the plastic knob is like the material on a model car, so this is not so far off target.

[Shop Rat]

I have had good results cleaning plastic with simple baking soda and warm water.

It is the only thing I have ever used that will take that discolored sort of sticky residue off of a child's plastic high chair tray after it has not been used in awhile. For some reason no matter how much you clean them, if they sit unused for awhile they get that coating on them. Baking soda and warm water will take it off and leave no scratches or residue.

[Rawja]

You could try soaking 'em in a hot concentrated Oxy-Clean solution, stuff works wonders and is incapable of harming the plastic.

[Guest Foggy norm]

I've had good sucess with discoloration using ZUD, then give the plastic a squirt of penetrating oil. Soaking works best if you have time. It is a cleanser, comes in liquid or old fashioned powder:which I prefer, for soaking.

This is excellent for glass items with rust stains. I put the item in a small dish/cup depending on size. Enough water to cover the item, and add the stuff, to cover the item, and leave it. It has abrasive which sinks to the bottom which I rarely use, and periodically add some more because of dilution. Plastic shouldn't require any lengthy bath and using your fingers with the abrasive would work like baking soda. If you use the liquid stuff, don't add water, it's better for items that can't be soaked.

[Guest Foggy norm]

The closest to white, really, that I've seen was on a Packard 53 convertible.

[Ron Green]

Any ideas on how to whiten Knobs that have turned yellow over the years? Presumably it is plastic from the 60's. Thank you in advance.

I use a plastic buffing compound for lenses, knobs, etc. http://www.eastwood.com/ew-buff-compound-plastic-13-oz-tube.html

If the knobs are too far gone I paint (with hardner) and clear coat. <O:p

[Guest Jim_Edwards]

A bit on this subject:

If you ain't old enough to remember what degree of white knobs and buttons were when they new don't assume they were something they weren't! None will ever be lighter or nearer white than they were to begin with regardless of what one might think. Best idea is to stick with mild cleaners to get rid of any crud and leave it at that unless you have a spare set.

Jim

[Ron Green]

To the best of my knowledge few knobs were “white” in the day. If it is ground in surface dirt typically cleaners won’t do the trick, especially if you are restoring to show. A little bit of research or a few phone calls and you will find the correct color and or shade.

Edited March 16, 2011 by Ron Green (see edit history)

[1929Chrysler]

I found the answer to my question and I am EXTREMELY happy with the results. After searching the web I came across "The Retro Project" in which a process was by chance discovered in 2008 in a German Museum and later perfected by English chemists. It was originally believed that the yellow discoloration in white plastics with age is permanent. NOT SO!! With a simple solution of Hydrogen Peroxide and Oxy-Clean mixed together while letting the parts soak under the sun (ultraviolet light) for about 8 hours my parts came out brand spanking new!! I'm not kidding. These parts were actually just as white as the new plastic on my kids toy. Google The Retro Project and you'll see the process.

[Restorer32]

Or did you bleach out the original color?

[Guest Jim_Edwards]

I found the answer to my question and I am EXTREMELY happy with the results. After searching the web I came across "The Retro Project" in which a process was by chance discovered in 2008 in a German Museum and later perfected by English chemists. It was originally believed that the yellow discoloration in white plastics with age is permanent. NOT SO!! With a simple solution of Hydrogen Peroxide and Oxy-Clean mixed together while letting the parts soak under the sun (ultraviolet light) for about 8 hours my parts came out brand spanking new!! I'm not kidding. These parts were actually just as white as the new plastic on my kids toy. Google The Retro Project and you'll see the process.

How about a link to the specific site. Seems google returns about 9 zillion "Retro" sites including dozens inclusive of the word "Project."

Jim

[TG57Roadmaster]

Here's the link to the Retr0bright Project that discusses the whitening process.

I'm going to try it on some '56 Lincoln window switch knobs

(notorious for yellowing) and report back.

Look here for the actual formula/process.

TG

Edited March 20, 2011 by TG57Roadmaster (see edit history)

[Guest Jim_Edwards]

Or did you bleach out the original color?

Exactly! Hydrogen Peroxide unto itself shouldn't alter anything. One hell of a germ killer/sanitizer and general cleaner though. We, along with every doctor's office and hospital use a 50/50 mixture of water and common Hydrogen Peroxide found on grocery and drug store shelves for those purposes.

Honestly without a brand new example of any plastic knob material that could not under any circumstance suffered appearance change from age how would anyone know the degree of "white" a knob or button would have been or should be? As others and myself have pointed out, few if any knobs or buttons made of plastics of some nature were absolutely white in the first place. Off white or an Ivory yes. White as a new dress shirt, no.

The Ford and Mercury cars of the 1940's probably had the most extensive use of a light color plastic on their dashes and none were ever bone white even when new. Those plastics were made from soybean oil. Henry Ford was real big on the idea of using materials that could be produced on the farm and at one time Ford had some 60,000 acres of land planted in soybeans to support their use of plastics made from soybean oil.

Jim

Edited March 20, 2011 by Jim_Edwards (see edit history)

[Guest Jim_Edwards]

Here's the link to the Retr0bright Project that discusses the whitening process.

I'm going to try it on some '56 Lincoln window switch knobs

(notorious for yellowing) and report back.

Look here for the actual formula/process.

TG

I'd try that only on "junk" switch knobs. The formula on that web site is apparently suitable for use with more modern thermoplastics and those plastics found on that '56 Lincoln may not be of that nature considering that Ford may have still been jacking around with synthetic materials made from soybean oil.

I would point out that most of what we tend to identify as plastics on anything produced before WWII was not, repeat was not, the same as any of the modern thermoplastics. Most were pulp filled resins; resins of a totally unknown composition. Pulp meaning the solids were produced from wood and the reactions that might take place with those non thermoplastics when exposed to various chemicals may not be at all desirable.

Jim

[1929Chrysler]

The mixture does NOT alter the plastic in any way. It only attacks the Bromine molecules within the original Brominated Flame Retardants that were added to the plastic when it was new. These Bromine molecules are vulnerable to ultra violet light and will turn "yellow" over time. The mixture/process reverses the yellowing and does nothing to the original plastic.

You are assuming these knobs are from an automobile. They are not. The restoration project I am working on has knobs that were originally "white" and even if they weren't originally bright white the process would still restore the plastic to the original "off white" or "ivory" color of many automobile knobs without disturbing the original color of the plastic as outlined above.

[1929Chrysler]

To add to Jim's point. I would only try this process on knobs that you KNOW are plastic and I would be curious if any one out there would be willing to try it on old junk knobs made of unknown resins that are not made of plastic to see what happens.

[Guest Jim_Edwards]

The mixture does NOT alter the plastic in any way. It only attacks the Bromine molecules within the original Brominated Flame Retardants that were added to the plastic when it was new. These Bromine molecules are vulnerable to ultra violet light and will turn "yellow" over time. The mixture/process reverses the yellowing and does nothing to the original plastic.

You are assuming these knobs are from an automobile. They are not. The restoration project I am working on has knobs that were originally "white" and even if they weren't originally bright white the process would still restore the plastic to the original "off white" or "ivory" color of many automobile knobs without disturbing the original color of the plastic as outlined above.

I think that virtually anyone would have presumed you were attempting to "whiten" knobs found on automobiles given this is an automotive site and there was no mention otherwise.

Hopefully, no one will fire off and perhaps permanently damage plastics found on automobiles produced before 1950 or there about or from not knowing specifically the nature of the plastics/knobs on their automobiles which may or may not contain bromides intended to be fire retardants.

Jim

Edited March 20, 2011 by Jim_Edwards (see edit history)

[Guest bkazmer]

Amen Mr Edwards! Generalities about "plastic" are ill-informed. Antimony oxide is at least as common a flame retardant. And anyway, the standards required today for flame retardancy were not in place then. I think a more likely chemistry (but it is an educated (?) guess) is that the yellow is a degraded phenolic. Many early knobs used phenolic type plastics. Peroxides are not at all inert to plastics - they are sources of free radicals which initiate reactions. The degradation products of phenolics are often yellow and the subsequent reaction with free radicals turns them into a white material, but not the original chemical.