Acrylic scratch removal (while tank is running!)

[Dan H]

So a few days ago I was cleaning my tank with the magnet scraper, and when I rounded the corner of the tank, the scraper smashed a tiny snail and I didn't notice... So I gave a good long push and made a very substantial scratch that was about 8-10" long! Needless to say I was really sad to see such an eyesore on our tank. So I read up on the good ole internets on how to fix scratches while the tank is still running.

Here is the scratch:

Step 1 - Acquire waterproof sandpaper of grits 400, 800, 1200, 2000, 3000, 5000, 7000. I purchased 3 kits on Amazon that had various grits so I have plenty to choose from.

Step 2 - For the scratch, depending if it's really deep or not, use either the 400 or 800 grit. I used 800 on the scratch above because I was scared of the 400. Cut a small square that is about the size of your fingers.

Step 3 - Using almost no pressure, hold the sandpaper with your fingers as flat as possible and gently move back and fourth (or up and down) across the scratch. Go perpendicular to the scratch (90 degrees). You only need to do a few passes across the entire scratch.

Step 4 - Cry because now the acrylic will look like you really just messed up.

Step 5 - Calm down, and get the next higher grit, and cut another square. Go perpendicular to the direction of your previous grit sandpaper. Again, with minimal pressure, hold the sandpaper with your fingers flat, and move back and fourth (or up and down). You only need to make a few passes over the section.

Step 6 - Repeat Step 5 until you get to 7000 grit.

Step 7 - With the 7000 grit, I first went perpendicular to the previous grit. At this point as you sand you can feel the paper resist where it needs more sanding, and it will be very smooth where it's sanded enough. You will see a soft white cloud of acrylic coming off where it still needs sanding. You may have to get a new square of sandpaper if it clogs up.

Step 8 - Use a new square of 7000 grit, and go perpendicular to your previous pass with 7000 again. You should get the entire section/panel to be smooth as possible when passing over it. From the outside, you might see a very slight haze on the acrylic. When it's smooth, the sandpaper will pass over and you won't see any acrylic "dust" coming off, and it will pass by with almost no resistance.

Step 9 - Go over the panel with your magnet scraper, and any remaining haze should go away. If you still see any haze/lines, you may have to sand a little more with 7000, try going 90 degrees again if necessary.

Step 10 - Grab a beer and enjoy your restored acrylic.

Finished:

A lot of the internets was suggesting that 2000 was sufficient but I found that you could still see very substantial lines and it was hazey. I wasn't able to get it to be a mirror finish until I did 2 passes with the 7000. 1 pass just didn't cut it. After the second pass, It was such a good finish that I think it actually looks better than when I originally bought the tank. Perhaps the manufacturer didn't even go to 7000?

I know everyone is scared of acrylic because it scratches easily, but in less than 3 hours, I was able to polish the entire tank and have it restored to better than new. Granted my arms are pretty tired now.

[Dan H]

I forgot to note that for re-finishing the entire tank, I only used the 3000, 5000, and 7000. It wasn't quite enough to remove some of the slight scratches, but it removed about 99% of them and all of the original polishing marks are gone. The remaining few scratches I'll probably have to go down to about 1200 or possibly 800 for 1 or 2 of them to really buff them out.

[LarryD]

This is the same process that is used to achieve mirror finishes on metals however most of the time (and I believe the acrylic tank manufactures do the same thing) instead of using the extremely fine sand paper to finish it since it clogs up so easily they will use a series or polishing compounds to achieve the final finish. This also saves the arms because you usually use a cloth polishing wheel on a power tool. However because it is being used in water the paper would tend not to get loaded up and all you would really run into is the paper wearing out.

You are lucky it only took 3 hours I have spent days doing the same thing on metal, even ones as soft as silver and that was using power tools to finish it.

[Dan H]

Yeah, I would suspect if there were a lot of substantial scratches, it would be a lot more effort. The scratch in the picture above was the only real significant scratch that you could feel with your fingernail. The rest were all superficial and buffed out very easily. It would have been nice to polish it with some Novus, but since it was filled up all chemicals were off the menu obviously.

The 7000 did clog up pretty quick. The good news is since you're working on clear acrylic, you can actually see it get clogged up, plus you can feel it.

I believe this is also a similar process used to polish scratches in car paint. I'm half tempted to read up and give that a go in the future. Then again, probably not.

[mFrame]

Nice job and nice writeup. I only wish it was that simple for glass...

[Dan H]

Nice job and nice writeup. I only wish it was that simple for glass...

Another reason to get acrylic next time.

[jestep]

I tried to resurface a whole cube tank a few years back. It has substantial scratches inside and out over about 80% of the entire tank. Most were more of light scuffs but had a few deeper ones. Had a air powered buffing pad, and the 3 part novus compounds, and I eventually gave up after about 10 hours of work maybe getting through 30% of it. I'm sticking with glass even though it's almost impossible to get scratches out of.

"A scratch", no problem, buff it out. Entire scratched tank = find a new tank...

[mFrame]

Take a look at Dave's (dapettit) acrylic restoration thread if you want to see just how bad a tank can be scratched and end up beautiful with a LOT of work.

[Reburn]

Dan,

Great write up and great job!!

I'm gonna stick with glass though I'm lazy. Plus it's harder to scratch.

[Dan H]

Glass is indeed harder to scratch, but much harder to fix scratches... Sometimes impossible. And if you have low iron glass (Starphire) it actually scratches fairly easily... Still not as easily as acrylic.

The ultimate lesson here is look carefully for those little snails... And don't accidentally crush them with your magnet scraper. Especially if you have to use a really powerful magnet.

[Isaac]

Same process w/ glass, just takes much more force and time. Mush easier to drain and use powertools.....sooo i live w/ mine. Good job on your fix!

[Timfish]

I much prefer buffung out scratches in a dry tank because you can use a orbital sander or buffer but as Dan has pointed out using various grits you can get really good results without draining a tank. I also go to 9000 grit for the final step.

[Dan H]

Oh, may have to get some 9000.

[+brian.srock]

I may have to give this a go one of these days as I have a low iron front with a couple good size sand scratches and if its as easy to work on as acrylic that'll be awesome.

[Dan H]

I have no clue if it works on glass. I would suspect so, but it would seem like the amount of elbow grease would be substantially more considering it's a lot harder material.