How to: Fix scratches in clear plastic parts!

[Sebstar]

Okay, im writing this because i just had lots of glue tip on my windscreen and after having a nervous breakdown i recalled something the dude at the local hobbyshop said :P
He said he dropped his car and something happened and it scratched the shit out of his clear parts. He then mentioned that he sanded it down and used toothpaste to fix it up.

Well, anyway. This doesn't have any pictures because its a simple thing to do!

Please be warned: this will not COMPLETELY fix up the window, but make it pretty darn close to perfect

1. Use a high grit sanding paper (i used 2000 and thats why theres still some scratches visible) and sand down the area that needs work. This works perfectly if you accidentaly cut the clear part with a modelling knife. Completely sand down the area, but be careful. Casually increase the grit # until the scratch is no longer visible.

2. Now the clear part will look FUBAR, don't worry, it won't stay like this forever! Use a polishing cloth (i used one that scratched my car, so maybe thats why my attempt still carries a few imperfections), and either use compound or toothpaste (toothpaste is a mild abbrasive so it will cut!). Lightly rub the compound into the clear part that needs the fixing. Once the first layer is done, wipe it off completely and repeat the rubbing part until satisfied.

3. Lastly, wash the part quickly in some tap water. The area should be clear now! If result isnt as desired, repeat from 1.

Be warned however, i strongly suggest you try this on a spare or broken piece of clear part before! I thought it wasn't too bad a mistake for my car, so I went along with it, but if you want a perfectly see through-without-scratches windscreen, i suggest you order that particular tree again.

I hope this helps some people who are upset over a big scratch and think it cannot be fixed.

See ya later!

[Zcaithaca]

wow that seems pretty good! do you have any befroe and after pics

[Sebstar]

hm, ill post some tomorrow. its late and the camera is in parent's room. I dont have a pic of what it looked like after the spill, but I have a pic comparing the original clear part to the fixed up one (please note i did not spend much time fixing it up)

[Sebstar]

Okay, here we go! The car pictures didn't turn out very great, so you can't see much there
BUT! I found another test object, my trusty Coca-Cola ruler!
Please note this was like a 10 minute job, and with higher grit sand paper, this would have looked quite perfectly :P

Required tools for this procedure:
Sand Paper (from about 600Grit to around 2000 - if you have grit such as 12000, work your way up to that)
Polishing cloth
Compound or Toothpaste
Time (this job took me about 10 minutes, im sure higher grit and more time would have gotten a much better result)
PS, I dont think this camera has stability control, lol. (i appologize if you get a bit nauseous)

Here we have the subject in a very tricky situation. Some glue spilled on it and made it look all crap (please note my car windows had paint on it as well, thus making it look even worse)

The spill might not look so bad in these photos, but believe me, it was quite horrible

The next photo shows the area sanded with 600grit paper

I skipped 800 grit and 1000grit and went directly to 1200 and the image shows 2000grit.

The next photo shows the first layer of toothpaste (i did this to see how effective it would be)

After 2 coats of toothpaste and 1 coat of compound, the result is as follows:

Here, finally after about 4 coats of compound and 2 coats of toothpaste, the result looks like this. Also in this photo you can see what the 600grit sanded area looked like, and there is still a bit of a sign of the spilled glue. As I said previously, with more time and better wet&dry, this would have looked much better!


I hope this helped you somehow in fixing your clear parts, BUT BE WARNED! Do this whole process very carefully! The ruler I used was about 4mm thick...

PS: The ruler on the sanded and compounded area is now much cleaner than the other parts, lol

[tdoty]

2000 grit? I start with 220!

The whole point of polishing is not to remove the scratches, you're actually making them smaller and aligning them. The biggest thing to watch is that all of your sanding follows EXACTLY the same direction!!!!!!! You want all of the little lines going the same way - if a few strokes are in another direction, the scratches will be clearly visible. The 220 grit gets down to the material below the visible scratches, and does it quickly.

You can start with 1500 or 2000 grit, but it will take a bit longer to get out the deep scratches. I start with 220 (wet, always wet) to remove the material above the scratches. Then switch to 400, then 600, then 800, then 1200, then 1500, then 2000. That gets followed up by Meguiar's Show car glaze. It sounds like a lot of work, but it only takes a minute or so with each grit to do a windshield.

Sometime soon I'll post pics of the windshield for my C5R custom. I used the method I just described to remove the brace from the inside of the windshield. The same method can be used to help remove the "waviness" from kit glass - a good blast from the sandpaper and the waviness is gone!

It is also a good idea to back the "glass" up with some modeling clay. The clay helps support the "glass" so that it doesn't crack - I haven't found a good way to repair cracks in kit glass without replacing it completely.

Hope this helps some,
Tim D.
http://modelcartech.com

[Sebstar]

i started with 600 grit, which was more than enough for the problem presented.... oh yeah, and ALWAYS WET SAND when you do this!

[VnnyDaPooh]

Also, once you get it down to very fine scratches, just dip it in Future. It's an acrylic floor polishing liquid. Once you dip it, the future will put a smooth layer of acrylic on and fill up the spaces in-between the scratches and will give it that permanent wet look. Works wonders for winsheilds.