White color coil question. Anyone restore a yellowed coil?

[megadivers]

I have a few coils that are absolutely perfect but have yellowed over time. Does anyone know a way to restore the color? Anyone know why some coils do this and others do not? I spoke to a manufacturer earlier this week and they didn't even know.....

 

[UK Brian]

Its just the effect of sunlight that kicks it off but once started it seems to get worse even if the detector is kept in the dark. Some manufacturers coils are very bad for this, others don't seem to be affected.

I tried various cleaning products including those with bleach content but they only lightened the effect.

Prevention is best so after cleaning a coil I always pop it into a black bag.

Funny to think many of the early plastic coils were black, green, even brown and there was a big movement to paint them to reflect the suns heat and help maintain detector stability. Now there seems to be more black coils than ever.

 

[shortribs]

Wonder if oxi clean would work??? shortribs

 

[Walknstik]

Krylon makes a paint that comes in a spray-can called Krylon Fusion which is specially formulated for painting plastics. I have used it for repainting plastic splash guards on a Jeep and it's held up well through the years.

 

[Sven]

Use this right from the start to prevent yellowing 3M 303 Protectant

http://www.detailedimage.com/products/auto/303-Aerospace-Protectant-16-oz_12_1_m_3994.jpg

https://www.youtube.com/watch?v=9J4yF3OpYZQ

 

[Mega]

Never had any trouble myself with white coils going yellow,but one brand name thathad this problem was the Arado 120b and possibly the 130 as well,i have 2 mint condition ones and they are still perfect white,i do keep them away from sunlight in a cupboard as this seems to have stopped them yellowing.

Also have a few other white colour coils for my DFX and Tesoro detectors but the yellowing does not appear to be a problem and they are still perfectly white,will admit though the 2 Arado machines are 30 years old,so although mine are all right it must be a age related problem.

 

[Sven]

Plastic has changed over the years to help white from yellowing by adding UV inhibitors.
And I believe white was used because it doesn't absorb heat as black coils. And on some older machines as the day warms up with sunshine, the coils
warm up as well and the machine's tuning starts to drift. Then you would have to adjust for it.

To play it safe, yellowing is ugly, manufacturers make the search coil color black.
But for water machines white or yellow are the best, you can't see a black coil in murky water.

 

[UK Brian]

Sunlight affects the fire retardent present in some plastics which causes the colour change.

I've tried several things lately some of which didn't work at all (like baking soda).

Best is a little complicated in needing more than one chemical. Check RetrOBright project on the web. Chemicals were much cheaper than expected off E-Bay.

 

[Sven]

I did find on some plastics, bleach works well. Or Comet clenching powder. Works on older Garrett coils.

 

[megadivers]

Looks like after reading quite a bit, the bleach method works but can cause the pastic to become brittle. I will be assembling the ingrediants for the retrobright formula and let everyone know how it does.