Getting a good finish on Acrylic?

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Scooley01

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College Station, Texas
I love turning acrylics. There are amazing colors and designs out there, and they can really turn out stellar.

I've had a problem as long as I've turned them, though, that I just can't seem to solve. After I've done everything I can to polish the blank, I still have very faint (VERY faint) circular marks. They're typically only visible when you have a good light reflecting on the pen, and they're very fine scratches, but I hate it!

So I wanted to put my method of polishing up here, and see if maybe I'm doing something wrong.

To start, I sand using paper (on rolls from PSI). I typically start with the 320, but it depends on how rough the blank is after turning. I do the 320, stop the lathe and look for any deep scratches it might have made, and sand lengthwise with the lathe off to get rid of those. Then on to the next grit (400), and stop and sand lengthwise, then 600 grit the same way.

Then I take a paper towel (Scott's Rags in a box) and dampen it, and wipe down the blank to get all the dust off.

From here, it's wet sanding with my MM. I have the MM sitting in a tupperware dish of water, so they have a lot of water on them. I use the sanding pad in one hand, and a paper towel to dry the blank between pads in the other. I go through each grit, usually I skip the first one (600) because it's too rough and does more harm than good. I check the blank in between each grit to make sure it's sanding well, I'm not missing spots, etc.

After the MM, I use One-Step polish from PSI. I know One-Step's instructions say sand to 600, then polish, but I find the surface is much nicer if you use the MM before the One-Step. I take a folded up paper towel, and run a line of One-Step out of the bottle along the blank. I rub it in somewhat with the lathe off, then turn the lathe on. I wipe for a second, then switch to a clean part of the towel to buff the One-Step off. I do this 2-3 times.

The surface is really shiny for the most part at this point...with the exception of those tiny scratches I mentioned. I tried to get a picture but they're too fine to photograph!

So am I doing something wrong here that's causing these marks? Or are they just a by-product of a handmade product and they're normal?
 
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Good Morning Scooley,

It seems to me your are doing everything correct and in some steps you are going beyong what is recommended, but my question here is you are calling "buffing" your blanks (then switch to a clean part of the towel to buff the One-Step off. I do this 2-3 times).Usually those "micro scratches" go away when you run your blanks thru a buffing station with Tripoli and diamond compounds althought I use the compounds from caswell for this process.Check out ed4copies video on buffing HOW TO #8--Buffing.mp4 - YouTube
Maybe this will help
 
I was afraid that might be the answer...it's the only thing I know for sure I'm not doing that I could be. I just need to break down and buy some buffing wheels for my grinder and the right compounds :\
 
Scooley01 said:
I love turning acrylics. There are amazing colors and designs out there, and they can really turn out stellar.

To start, I sand using paper (on rolls from PSI). I typically start with the 320, but it depends on how rough the blank is after turning. I do the 320, stop the lathe and look for any deep scratches it might have made, and sand lengthwise with the lathe off to get rid of those. Then on to the next grit (400), and stop and sand lengthwise, then 600 grit the same way.
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You mentioned wiping the blank off inbetween the MM. Do you wipe off the previous grid with the sand paper? You might be getting the particles inbedded in the acyrlic. Just my $0.5.
 
Absolutely agree with ashaw that buffing is the way to go but, in the interim (until you get a buffing setup), you might try switching from paper towels to a soft cloth when applying your polish. Granted, paper towels differ somewhat in their softness depending upon the brand you are using, but in the end they are all made of the same thing (wood fibers) and thus could be imparting very fine scratches to your pens.
 
A couple of questions, what speed do you sand at and do you change speeds when you polish. I always sand at the slowest speed try to avoid heat. but when i switch to polish i swich to full speed lightly appling pressure with the polish then switching to a clean part of the cotten rag and appling more pressure you should feel some heat from the friction. I have a beall buffing system but never use it on pens i find I can get a glass like finish with the polish.
 
I was wondering if passing on the 6oo you might be leaving some imbedded scratches behind..I go through every grit, know it takes a while but why skip 1? Have a bright light and check very closely between grits for any radial scratches..I finish with a couple coats of huts ultra gloss, then a lateral application of renaissance wax...works for me! Good luck!
 
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Steven - Good advice here. Although it's been said above, there are a couple points above I'd like to reiterate. First (important) - keep your water clean. Second is speed. Slow down a little. Third is pressure - don't apply much. Fourth is the "cloth" you're using - I cut up old 100% cotton t-shirts into small (4"?) squares. Discard them after (one?) use.

One other thing - I used (and will continue to use) PSI One Step. But lately I've been experimenting and found real success with Novus and Meguiar's Plastic X. I start with Novus 3, then go to 2 and finish with Plastic X.

Hope this helps
 
If you have all the MM pads sitting in the same bowl of water you might be getting grit particles from the course MM onto the fine grits. Just a thought.
Scott
 
What I've found that works pretty well for me is jewelers rouge while the piece is still on the lathe. Work it up thru MM and then rouge while turning about 2000rpm. It may not pass the 10x loop test but to the nekkid eye they glow!
Dave
 
Something I found helped tremendously was always - always - going longitudinally to finish with any grit of abrasive, whether it's sandpaper or MM or polish. You mention that you do this with the sandpaper, try doing it with the MM and polish as well.
 
I use the plastic polishing kit from CSCUA and others. After sanding to 600 I switch to the plastic polishing pads and use the last 4 grits wet, the pads are color coded and about 2" square. Then polish with Meguiar's Plastx, available at an auto supply store. It's the polish used on the million dollar canopies of jet fighters to remove scratches works great. I can buff with white diamonds, but rarely have to on plastic or CA.
 
ashaw said:
my last step is to do a final buffing. That will remove all scratches that can be seen under a 10x loop. I use this one Acrylic Pen Buffing System at Penn State Industries

I had the same problem until I started doing buffing as final step.
Click to expand...

How do you like PSI's system? I checked it out online, but since it used a different buffing compound that I'd never heard of, I was going to go with White Diamond on the grinder...
 
Here is what I do. IMO the key is the sloppy wet sand paper. Until i started getting lots of water on the sand paper I had serious issues with micro scratches.

1-sand through 600 not missing any grit only using sloppy wet sand paper at low speed. Use a paper towel to remove slurry after each grit.
2-Apply rubbing compound (3m) at low speed then jack it up. Buff it off at high speed. This shows the scratches and if I need to resand
3-Go through the colored pads all sloppy wet.
4-apply 3m rubbing compound again then jack it up and buff it off with a paper towel
5-3m finesse it at low speed to rub it in then jack it up to buff off
6-put on McGuires (sp) quick wax after close up inspection.

There are cheaper rubbing and polishing compounds on the market but this is what I had in stock from the high end boat detailing we did on occasion.
 
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I will confirm what Mark said. Low speed (400RPM) wet sanding. Sand lengthwise with each grit and MM too. Put something water-proof over the ways to keep water off them.
 
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