My windshield replacement saga is in it’s third of fourth year. First I had to get it made on the other side of the world (actually two of them), then I had to collect the box personally, then I had to carry it as excess baggage. Now I’m waiting for the only guy I trust to do the job to free himself from a series of ‘more interesting’ projects 
No it’s not a common type, no it’s not a simple installation compared with many common types, and no I’m not complaining. This is fun and games, part of the process of owning a plane and part of why I enjoy owning and improving stuff.
On the other hand, and closer to on topic, I’ve known a number of people who spent a day polishing their windshield who were very happy with results and no longer felt the motivation to get a new one. Sometimes you can get very satisfying results. I once made a windscreen look perfect starting a rasp and then 40 grit sandpaper…
I wish mine fell into that category but after 50 years it’s a little hazy right through the material and no amount of polishing will remove the haze.
A lot of older airplanes’s windows become less than 100% transparent over the years. Loads of them get scratched one way or the other.
I’ve heard that there are methods to clean those, be it with a particular chemical or with polishing. But I can’t find much of a reference on just how to go about it?
Any experience here in the Forum?
Scratches in acrylic (Plexiglass or Perspex) can be polished out, starting with wet sanding if necessary, then polishing with progressively finer compounds. It’s hard work even with machine polishing but if scratching is the only problem it works well.
Milkyness in acrylic goes through the material and cannot be removed in my experience. I’ve got a new windshield waiting to be installed for that reason.
If the transparency were made of polycarbonate (Lexan) it cannot be polished and will be ruined if you were to try. However aircraft transparencies are generally acrylic.
Thanks Silvaire. Good information.
Surprisingly good results can be had by flashing the surface with a blow torch!
Blowtorch handled by a very skilled and experienced operator?
I shared with an artist guy who had no fear when tackling perspex.
https://gcabrasives.co.uk/product/micro-mesh-kr70-acrylic-plastic-restoration-kit/
This is the one I’ve used, but to do a large area like a whole window may take a full day.
I did a Robin canopy with localised deep scratches, some very light (dirty cloth) type scratches over quite a bit of it, and a bit of overspray from someone.
That took a whole weekend.
Stickandrudderman wrote:
Surprisingly good results can be had by flashing the surface with a blow torch!
Please don’t do that. Flame polishing introduces internal stresses in the acrylic, which may lead to cracking – in particular, it will most likely crack if you later wipe the window with alcohol (for example, to remove ice).
Silvaire wrote:
If the transparency were made of polycarbonate (Lexan) it cannot be polished and will be ruined if you were to try.
It is possible to polish polycarbonate, search the web for restoration of polycarbonate headlights. I am about to do this on my car and will report the results.
We once had a Citation windscreen polished.
That decision subsequently cost us around $40,000 when the windshield had to be replaced due to the distortion caused by the polishing.
As already mentioned.“milky” forget it and get.a new windscreen.
Scratches in perspex I have seen three methods used successfully.
1) aluminium foil ( but only seen it use on the plastic headlights etc). I don’t know if I would use it on my aircraft windscreen unless I tested it first.
2) Brasso if that’s the one that comes with the wool. Gentle movements no scrubbing letting the wool do the work.
3) Toothpaste on a soft damp cloth.
Whilst writing this a friend has just mentioned a 4th.
4) Ash from a wood fire. Filtered so it is just the fine ash again applied gently on a soft damp cloth. Avoid circling motions as you run the risk of the windscreen blooming when flying into direct sunlight
My recommendation would be to test a small area before going at the area in front of your face.
