Thanks for the info Chris, I have not yet tried the vapour method. I think that might be a more controlled delivery, so will probably try it later. Acetone's boiling point is 56°C so wouldn't need a lot of fancy equipment, but it is too hot to hold without insulation and I hate to think what it does to the skin at that temperature
. I took a look at the method on YouTube and then eBay, I see they use a metal, 12 Volt, heated, thermal insulated car mug and a plastic 'funnel' thing as a spout - good plan.
Here below is the best demonstration / explanation of what I am doing. Although all my extra rubbing down is to ensure absolute removal of the yellowed, degraded, UV film and damaged polycarbonate underneath it. I'm getting as near as perfect a mechanical surface as I can, as my starting point. That's because this doesn't seem to have been done before, based upon the strength of the remaining, unaffected coating that I'm having to remove to get to a uniform surface. That's because the coating may not react the same as the polycarbonate of the headlamp. Also I'm removing many of the abrasions and scratches that result from 20 years of normal wear and tear. Next time will be much easier. I am also not happy to do this with the headlamp(s) in the vehicle.
Anyway, I have some more results from yesterday's session. Some good some bad, all part of the learning curve ! First of all I have a confession to make, I don't know how I could be this stupid. Towards the end of all my sanding I started to see yellow coming off again. It is a telltale sign that I'm sanding an area that needs more work. I was on a high grit and thought this had all been removed already. Well it had, what I was seeing was blood ! It never occurred to me that if you fold abrasive paper over, that you are in fact also likely to sand your fingers ! Well, I had already removed a couple of cm2 of skin ! Simply unfolding the paper made things easier, I will remember to put fingers to backing paper at the start in future. Later on when using the acetone, I cannot quite describe the pain ( yes, I know, PPE, what a plonker... )
Due to the difficulty in getting a clean 'pass' with the application of the acetone, I considered spraying it on. I wasn't sure what sort of bottle this would need so as not to dissolve. I do have a 'Touch-Up' gun, but the nearby compressor is not oil-less and the portable one would be a pain to extract. I settled for a holiday / airport cosmetic spray bottle, this didn't like the acetone on the polished outer surface, but otherwise was ok. However, it didn't work as expected, it simple cleaned the surface and left it looking cloudy. This was going to require waiting before I could rub it down again ( which might need some skin to regrow too... ). So I decided, 'in for a penny...' - I might as well try tipping it on ! Epic Fail... This went a brilliant, perfect surface for a whole 2 seconds, before going completely opaque. You can see a sort of 'High Tide' mark.
This puzzled me for a bit, but then I remembered that in the early days of courting my wife, I helped paint her boat ( she is an accomplished sailor and I, a mere midshipman, but I have my uses with ropes and sails when instructed ). Now her family is about as non DIY as is possible, she thought bizarre things like - once a wood screw was removed it wouldn't go back in again? Her dad ( primary cause of said confusion ) once put up a bookshelf and she was later scolded for putting a book on it, as it immediately fell off the wall. Anyway, the point here is that we did the job 'properly' as I am so inclined, and all was perfect until it came to the final coat. Now you don't paint a boat indoors, and this sort of thing takes all day, so it was getting late by the time we finished, but job done, clean brushes, down the pub ( Adnams btw ). Next day, instead of a fantastic gloss, we had a perfect MATT finish !
What had happened, was that it was a damp night and as it was drying, condensation had formed on the still soft paint. This had created microscopic pits where each spherical droplet formed and thus it was not flat or shiny - bu993r ! So I think this is what happened to me with pouring the acetone. The surface melted, but didn't get washed over by a cloth, using it cold, it gets even colder as it evaporates, almost like a freezer spray, so condensation moved in briefly and created the same effect. Nothing lost except some time, so re-sand today and try again.
In the meantime I thought I might as well experiment as I had already ruined the finish. So I tried 'wiping' over the rest of the lens
AND the cloudy bits. Conclusion, the rest worked fine, but the cloudy bit only improved marginally.
Also, these turned up today, must have been UK stock, literally only 2 days: £8 off eBay and the first of several orders I am now expecting for under bonnet and wheel arches, trim etc...
