|
||
|
17th January 2020, 08:45 | #1 |
This is my second home
75 Contemporary SE Mk II 2004 Man. Sal. CDTi 135ps, FBH on red diesel, WinCE6 DD Join Date: May 2010
Location: Leeds
Posts: 17,273
Thanks: 2,160
Thanked 2,061 Times in 1,586 Posts
|
Headlight polishing update
In August of 2019, I decided to carry out some long term experiments to solve the issues with my MkII's opaque headlight lenses. https://the75andztclub.co.uk/forum/s...highlight=lens
To test my theory I scrounged a gash Mk I lens from a local member. Idea was to try ordinary clear coat lacquer on on of the lenses on my Mk II and on the donated MK I lens, the latter being left out in the full sun and weather for a test period to see what developed. My Mk II spends much of its time in my garage, so hardly a fair test of deterioration. I began by thoroughly abrading both headlights down to bare polycarbonate, with course wet and dry, until I was certain all the original coating was gone, then polished them back up, with finer and finer grades of wet and dry, finishing off with a metal polish, before washing thoroughly. That, I followed with several coats of my clear coat aerosol. My finish proved a little disappointing, in that marks in the form of what looked like cracks appeared in the coating on both lenses. I managed to polish the worst of the lines out, before finishing with metal polish. Too the good - neither lens has shown any deterioration at all in the 6 months since I did them. When I have simply polished them up without any coating, the have deteriorated almost before my eyes in just weeks - so I'm that a successful experiment.
__________________
Harry How To's and items I offer for free, or just to cover the cost of my expenses... http://www.the75andztclub.co.uk/foru...40#post1764540 Fix a poor handbrake; DIY ABS diagnostic unit; Loan of the spanner needed to change the CDT belts; free OBD diagnostics +MAF; Correct Bosch MAF cheap; DVB-T install in an ex-hi-line system; DD install with a HK amp; FBH servicing. I've taken a vow of poverty. To annoy me, send money. |
17th January 2020, 09:28 | #2 |
This is my second home
Rover75 and Mreg Corsa. Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,751
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
|
Polycarbonate is very unstable to sunlight unless it's coated with a UV protectant. Spraying the repolished lenses with a UV stabiliser is essential or all your time and elbow grease will be wasted. I wonder how many of us actually do that?
TC |
17th January 2020, 15:19 | #3 |
Premium Trader
Rover 75 Join Date: Nov 2010
Location: Devon
Posts: 33,711
Thanks: 8,837
Thanked 14,831 Times in 8,030 Posts
|
It can also depend on how the lenses are moulded. A small decrease in mould temperature would upset the length of the polymer chains making them more prone to degradation than lenses moulded at the correct temperatures.
__________________
Lest we forget..
|
17th January 2020, 15:48 | #4 | |
This is my second home
MG ZT CDTi Join Date: Jan 2014
Location: carrick
Posts: 7,859
Thanks: 3,494
Thanked 2,657 Times in 1,973 Posts
|
Quote:
Perhaps also the uv reflecting of the surface of the polycarbonate to the inside of the clear coat cause issue? I understand the experiment is just a simple one, but could the questions above be even relevant or am I thinking too much into it. I have to say I find your experiments both engaging and fascinating. I and I am sure others appreciate the time and the effort you go to for them. Thank you. Sent from my SM-A600FN using Tapatalk
__________________
It is not gloss primer .............. it is duct tape silver! |
|
17th January 2020, 16:52 | #5 |
Avid contributor
Rover 75 Join Date: May 2015
Location: Leeds
Posts: 135
Thanks: 0
Thanked 17 Times in 11 Posts
|
Virtually all the lens polishing kits I have seen come with a protective clear coat that you are suppose to apply after polishing and then renew every so often.
Like you I have a MK2 and I used a standard headlight polishing kit to fix it. Not a showroom finish but I got allot of improvement. The trick is to be methodical and make sure you sand thoroughly with each pad. It is exposure to UV which clouds the plastic, so even if doesn't have a protective coat as new, it is sensible to apply one after polishing. |
17th January 2020, 17:17 | #6 |
This is my second home
All Trophy Blue ,ZT260#50 , ZT CDTI Auto, ZR105+ and 1.8T Firefrost spoiling the Set . Join Date: Nov 2006
Location: Nr Sherborne But in Somerset..
Posts: 6,061
Thanks: 916
Thanked 1,214 Times in 768 Posts
|
just as info, wifey Liz's lil Zr has plastic lens and being an 04 plater , its the same age and sits out in all the same weathers as the ZT's.But to date the lens are still pefect, not a spec of discolouring .
The 06 1.8T mk2 's lights are awful after a year or so since a polish session, the Mk 1 CDTi's are due for a clean as just one side has gone off since a polish a couple years ago. And the Mk 1 260 lights , again an 04 are still very good and never been touched So no rhyme or reason or nor particular model to blame So must be the plastic type and the makers ! C
__________________
The Three Bloo's Wifey's Zr105, MY CDTI & 260 #50 and Number One sons 1.8T in Firefrost When I were a lad Zero to 142 in 10.25 secs at the Pod on my Blown Norton. 210 Kart Champ in 70's Last edited by ceedy; 17th January 2020 at 17:23.. |
17th January 2020, 18:27 | #7 | |||
This is my second home
Rover75 and Mreg Corsa. Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,751
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
|
Quote:
Spotted this: Mold temperature has perhaps a less obvious but often more profound effect on final properties. In amorphous polymers such as ABS and polycarbonate, higher mold temperatures produce lower levels of molded-in stress and consequently better impact resistance, stress-crack resistance, and fatigue performance. Quote:
Quote:
I recently repolished my headlamps for the second time after not giving them any protection the first time. They're still off the car (SORN) until the weather warms up a bit. The expensive UV protectant I intend to spray on needs somewhat milder ambient temperatures than we have at present. Some polishing kits do come with a wipe-on type lens coating which I suspect is next to useless. They will give a very short lived UV mitigation, but you really do need a solid plastic film rich in UV absorbent to do a proper job. Even so, none of this is permanent unless you keep the car in perpetual darkness. TC Last edited by T-Cut; 17th January 2020 at 18:29.. |
|||
17th January 2020, 19:50 | #8 | |
This is my second home
MG ZT CDTi Join Date: Jan 2014
Location: carrick
Posts: 7,859
Thanks: 3,494
Thanked 2,657 Times in 1,973 Posts
|
Quote:
I have had those kits with the 'UV' protectorant. I have no doubt that it washed off lol. The ones I have used reminded me of Autoglym's extra gloss protection sealant, in its application.
__________________
It is not gloss primer .............. it is duct tape silver! |
|
17th January 2020, 19:59 | #9 |
This is my second home
R75 Saloon. Join Date: Feb 2009
Location: France/or Devon.
Posts: 14,003
Thanks: 3,851
Thanked 2,167 Times in 1,816 Posts
|
Perhaps Rover should have developed a pair of mechanical eyelids for use during the day.---Like these---
|
17th January 2020, 20:07 | #10 | |
This is my second home
Rover75 and Mreg Corsa. Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,751
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
|
Quote:
Yes, interfaces - the place where two layers touch - is a natural place for light reflection. Maybe a simple example, but the interface between a swimming pool's water and the air above produces a mirror at times and this causes internal reflections as seen by swimmers underwater. In the example you mention, the internal reflection is from the headlamp bulb's light traveling outwards and some being reflected backwards at the coating interface. This light will also get re-reflected outwards, but in spurious directions. It's that which creates flare/glare. In the case of a UV coating, the UV radiation is coming in from outside, so interfacial reflection will be back out again, so not affecting the polycarbonate further in. Interfacial reflections is why optical lenses for telescopes, cameras and such are given molecular-thin coatings of various materials to minimise image ghosting. It gives lenses a colourful caste when seen at a certain angle. TC Last edited by T-Cut; 17th January 2020 at 20:14.. |
|
Thread Tools | |
Display Modes | |
|
|