Polishing paint

[kymdlr]

This has been posted several times I’m sure . Looking for advice on what I’m doing wrong in the polishing process. Typically I clear my bodies, sometimes I’ll just polish out the paint without clear. Im noticing that regardless of compounds used, im getting fine lines in the finish that aren’t coming out.
 

My process is: 3200,3600,4000,6000,8000,12000 then scratch X, meguiars polishing compound, Meguiars ultimate polish then mothers carnuba wax. 

any suggestions?

[Chariots of Fire]

Either your sanding material has grit on it that is cutting into the paint as you sand or the paint is simply too soft to polish out.  If you have done a good prep job prior to sanding I would try not sanding the finish but just using a polishing kit or compound and then a polish but only after the paint has had plenty of time to gas out and get hard.

[jaymcminn]

What is your prep/primer process like? It's possible that these scratches are a result of scratching in the plastic or primer from block sanding. They'll tend to show up after the top coats have cured and shrunk down. 

Do these scratches show up regardless of whether you use polishing cloths or not? If it's only when you use polishing cloths then make sure you alternate directions when you go up a grit to help eliminate the scratches. Make sure you're using plenty of water with a drop of dish soap for lubrication. You might also be starting at a more coarse grit than necessary, scratches from 3200 grit can be tough to get out.

Finally, what are you using to apply your compound/wax? Do you reuse the applicator cloths? I buy cotton flannel by the yard at the fabric store and cut off a fresh piece for each polishing step, discarding them after one use. Micro-abrasives can embed themselves into applicator cloth and are difficult to wash out. 

Edited October 10, 2023 by jaymcminn

[Can-Con]

Sounds like your doing everything right. This happens to me all the time too.

You have to be careful not to get anything between the paper and the paint your polishing. Or sometimes a bit of grit from the paper comes free and makes scratches. 

Also, are you sanding in a different direction with each grit? that helps. 

When it happens to me I just start over with the finest grit that will get rid of the scratches and continue on.

[Nacho Z]

Ron, sounds like you have a good regimen for polishing your paint.  The three responses above mine are excellent.  I would believe that there is piece of grit causing havoc.  The only thing that I would add is do you really need to start at 3200?  Might not seem like a big deal, but I would try to eliminate the coarser grits as much as I could.  Just a thought.

[Dpate]

With regards to everything up top make sure you use a quality micro fiber or flannel cloth. Cheap micro fiber towels can leave scratches. 

[kymdlr]

1 hour ago, jaymcminn said:

What is your prep/primer process like? It's possible that these scratches are a result of scratching in the plastic or primer from block sanding. They'll tend to show up after the top coats have cured and shrunk down. 

Do these scratches show up regardless of whether you use polishing cloths or not? If it's only when you use polishing cloths then make sure you alternate directions when you go up a grit to help eliminate the scratches. Make sure you're using plenty of water with a drop of dish soap for lubrication. You might also be starting at a more coarse grit than necessary, scratches from 3200 grit can be tough to get out.

Finally, what are you using to apply your compound/wax? Do you reuse the applicator cloths? I buy cotton flannel by the yard at the fabric store and cut off a fresh piece for each polishing step, discarding them after one use. Micro-abrasives can embed themselves into applicator cloth and are difficult to wash out. 

I prime and wet sand it down with 3200, 3600 at the most and shoot color over that. I do use microfiber cloths or an old T-shirt with my compounds but switch spots on the cloths with each pass of compound. 

[kymdlr]

1 hour ago, Can-Con said:

Sounds like your doing everything right. This happens to me all the time too.

You have to be careful not to get anything between the paper and the paint your polishing. Or sometimes a bit of grit from the paper comes free and makes scratches. 

Also, are you sanding in a different direction with each grit? that helps. 

When it happens to me I just start over with the finest grit that will get rid of the scratches and continue on.

I’m thinking I need to spend more time with each grit to make sure each layer is doing what it’s supposed to. 

[kymdlr]

1 hour ago, Nacho Z said:

Ron, sounds like you have a good regimen for polishing your paint.  The three responses above mine are excellent.  I would believe that there is piece of grit causing havoc.  The only thing that I would add is do you really need to start at 3200?  Might not seem like a big deal, but I would try to eliminate the coarser grits as much as I could.  Just a thought.

It could be that the 3200 is too much to start with, which grit would you recommend as a starter and stopper? I’ve seen some guys starting with 1000.

[Nacho Z]

4 minutes ago, kymdlr said:

It could be that the 3200 is too much to start with, which grit would you recommend as a starter and stopper? I’ve seen some guys starting with 1000.

Hi Ron, I’m going to assume that you are using the Micro Mesh cloths.  When I paint I always try to make that last coat a heavier, wetter coat.  This seems to give me a smoother surface.  I generally start at 4000.  I have dropped down to 3600 to get stubborn boogers out, but 4000 is my normal starting point.  Like you, I run up to 12,000 and then I use Tamiya polishing compounds.  If all goes well, I will skip the Coarse compound and start with Fine.  Hope this helps.

[StevenGuthmiller]

1 hour ago, Nacho Z said:

Hi Ron, I’m going to assume that you are using the Micro Mesh cloths.  When I paint I always try to make that last coat a heavier, wetter coat.  This seems to give me a smoother surface.  I generally start at 4000.  I have dropped down to 3600 to get stubborn boogers out, but 4000 is my normal starting point.  Like you, I run up to 12,000 and then I use Tamiya polishing compounds.  If all goes well, I will skip the Coarse compound and start with Fine.  Hope this helps.

That's pretty much exactly the same approach that I employ, although the compounds I use are different, but that should hold little bearing on your problem.

My suggestion would be to start with a finer grit if possible, and above all, wait until the paint is completely cured.

Soft paint will be much more prone to fine scratches than a fully hardened paint.

 

Also, the more paint and clear the better when it comes to polishing.

Nothing worse than spending countless hours painting, clear coating and polishing only to burn through the paint with 10 minutes of work left to go!

 

 

 

Steve 

Edited October 11, 2023 by StevenGuthmiller

[jaymcminn]

1 hour ago, kymdlr said:

It could be that the 3200 is too much to start with, which grit would you recommend as a starter and stopper? I’ve seen some guys starting with 1000.

The grits on the Micro-Mesh system do not directly correspond with standard sandpaper grits. They use a proprietary scale. MM 3200 is more or less comparable to 1500 grit sandpaper. I start with the highest grit (least abrasive) possible to level out the surface... usually 6000 but I'll go down to 4000 if it isn't getting the job done. It's more elbow grease but you avoid the potential for the sort of deep scratches you're seeing here. Go up through the 12000 grit, which is the perfect starting point for Meguiars Ultimate compound and polish.

I would stay away from microfiber cloths for final polishing as well. Microfiber is TERRIBLE for holding onto old abrasives, random bits of grit, etc. and doesn't like to release this stuff even after washing. Old t-shirts are okay, but they need to be all cotton (polyester fibers are abrasive) and clean. Even then I'd be leery. My fabric store cotton flannel costs about $4/yard and a yard lasts me for a year or more. 

 

Edited October 11, 2023 by jaymcminn

[Nacho Z]

11 minutes ago, jaymcminn said:

I would stay away from microfiber cloths for final polishing as well. Microfiber is TERRIBLE for holding onto old abrasives, random bits of grit, etc. and doesn't like to release this stuff even after washing. Old t-shirts are okay, but they need to be all cotton (polyester fibers are abrasive) and clean. Even then I'd be leery. My fabric store cotton flannel costs about $4/yard and a yard lasts me for a year or more. 

 

Jason brings up a good point about the cloths.  I also use what Jason is talking about, cotton flannel, (at least I believe that is what it is).  My wonderful wife bought me a ton of it and it will last me many years.  I even go this far; I cut something like a 6”x6” square of it and put a little color dot in the corner of the square to correspond with the particular compound that I will use.  This way I will never “cross contaminate” the cloth with the wrong compound.  When I’m done polishing I will cut away the used area or just toss the whole thing.  Lastly, I have a 4th cloth just to wipe up an leftover compound or haze on the body.

 

[Bills72sj]

Here is a link to making scale "long boards" you can actually hold. I sand in a diagonal crosshatch pattern which is what professional bodymen do with 1:1 long boards. It gives you precise control approaching ridges. For polishing, I agree with the use once and throw away philosophy

.

 

[bobss396]

9 hours ago, kymdlr said:

It could be that the 3200 is too much to start with, which grit would you recommend as a starter and stopper? I’ve seen some guys starting with 1000.

With lacquers, I will start at 1500, if that is not cutting it, I'll go to 1200 or 1000. With the Detail Master cloths, I cut new ones into 4 pieces and mark the grit on the back with a Sharpie. If one piece gets beat up, I toss it. 

Color sanding I always do wet, I add a drop of dish soap to the water, it lubricates and keeps the cloths cleaner. If you ever feel something dragging... STOP. You should look at the cloth or sandpaper for grit or other crud they pick up.

I follow the same pattern across the body so I know where I had left off with the previous grits. I rarely go past 6000 grit, I use Meguiars or toothpaste to finish it off. At times, I may have to go back with a coarser cloth to get closer to an edge or crown line.

[Chariots of Fire]

Now that you have sanded through the color and primer you will have a rough time trying to correct the paint.  Your only choice now is to strip the body and repaint.  That spot will be very difficult, if not impossible, to blend in.

[bobss396]

On 10/12/2023 at 10:52 AM, Chariots of Fire said:

Now that you have sanded through the color and primer you will have a rough time trying to correct the paint.  Your only choice now is to strip the body and repaint.  That spot will be very difficult, if not impossible, to blend in.

A modeler's worst nightmare. I always make sure I have sufficient paint on the body, taking care to get the edges well covered. I start out with the body upside down to make sure the roll pans, etc have a good amount of paint on them.

For me, lacquers are more forgiving than softer paints. Earlier in the year I had an issue when I was into the clear coat polishing stage and had to go back and carefully shoot the color coat in one area. 

[StevenGuthmiller]

On 10/12/2023 at 9:52 AM, Chariots of Fire said:

Now that you have sanded through the color and primer you will have a rough time trying to correct the paint.  Your only choice now is to strip the body and repaint.  That spot will be very difficult, if not impossible, to blend in.

Exactly why I use ample clear coats.

As many as 5 coats in lacquer.

This ensures that there will be little possibility of "burn through".

 

 

 

Steve

[Skip]

This may sound stupid, so don't be upset if this is what you're doing. I haven't seen this addressed so time to ask...

Are you using adequate water to flush away the shed paint removed by the polishing pads or are you using the films / pads dry. The only time that I use polishing films or pads dry is correcting small dust bunnies in the paint. Otherwise, I flush the body with water with a drop of liquid dish detergent which helps the abrasive particles cut better and helps clear away the paint particles shedding off the body as you wet sand. Most hobby shop sanding sticks can be used wet or dry as well, makes them last longer.

[kymdlr]

9 hours ago, Skip said:

This may sound stupid, so don't be upset if this is what you're doing. I haven't seen this addressed so time to ask...

Are you using adequate water to flush away the shed paint removed by the polishing pads or are you using the films / pads dry. The only time that I use polishing films or pads dry is correcting small dust bunnies in the paint. Otherwise, I flush the body with water with a drop of liquid dish detergent which helps the abrasive particles cut better and helps clear away the paint particles shedding off the body as you wet sand. Most hobby shop sanding sticks can be used wet or dry as well, makes them last longer.

I wet sand. Just learned about adding dish soap from this thread so I’ll be doing that from now on. I stripped the body and going to start over.

[kymdlr]

I did some experimenting with another body that was polished with the same minor scratching in the finished result after polishing. I put a coat or two of future/ pledge liquid over it and surprise, scratches aren’t visible anymore and I have a nice shiny finish again. Sharing this tip in case someone could use it.

[Skip]

Another silly, probing, question please don't get upset if this is what's happening. Just trying to help here, that's what we are all here for in the first place to help one another be better modelers. Hope this helps narrow down your paint issue.

Since you said that the scratching occurred again on a second painted body, you are using wet sanding and flushing away the shedding paint residue.  The next thing to check is going to be your sanding pads / films / papers for contamination even slight.

Examine your polishing films, pads, papers... use a magnifying glass if you have to. Now, do you see any gummed-up paint residue on the polishing film? It will appear as a little roundish dot building up to a splotch on the polishing film/pad. If this is the case, the paint residue on your pad is probably your scratching culprit. Sometimes this buildup happens even with wet sanding while using a wetting agent such as a drop of dish soap. It pretty much signals that the aggregate media on the film is worn out - time to replace. (See Below **Bonus Tip - how to fix a good but slightly gummed up abrasive pad.) Next, after you are finished with all wet polishing, store the polishing kit in a baggie or container so it is not going to pick up contaminates while being stored. It sounds like there is some sort of contamination issue, just not sure where it is being introduced into your polishing process.

*Polishing Tip - Another hint taken from wet sanding more than a few full-sized cars is to use a dense foam pad to back up your sanding film / paper. I use the (3"X2"X3/8") McGuire's Black Foam pads that I cut down to size with a super sharp knife. I actually use a kitchen butcher knife to cut them, to get a straight square cut I take a piece of wood block a little longer than the pad set it on the pad and use it as a knife guide. The knife has to be really sharp to get a good smooth cut, the foam will tear otherwise. Then I use these Mini-Pads to back up the smaller sanding films and even the sanding pads while wet sanding / polishing. The foam pads control and distribute the pressure evenly across the pad. Use just enough pressure while polishing, so you feel just a slight drag, not a full-on cutting action like with sandpaper.

** Bonus Tip - You can maintain polishing films / pads with an art gum eraser, or the gum-rubber pads made for cleaning sanding disks, or to remove latex masking fluids (used by watercolor artists). Both the eraser and the cleaning pad can be found at a well-stocked art store, (or Dick Blick, Jerry's Artarama, Cheap Joe's websites). Both the eraser and cleaning pad are used just like an eraser on paper, best results are rubbing the eraser on the sanding pad in one direction until you get all of the embedded contaminants off of the pad. If you cannot get it 100% clean, then it's time to replace that pad / film.  This trick works to extend the life of sanding sticks and sandpaper on the bench as well.

[kymdlr]

8 hours ago, Skip said:

Another silly, probing, question please don't get upset if this is what's happening. Just trying to help here, that's what we are all here for in the first place to help one another be better modelers. Hope this helps narrow down your paint issue.

Since you said that the scratching occurred again on a second painted body, you are using wet sanding and flushing away the shedding paint residue.  The next thing to check is going to be your sanding pads / films / papers for contamination even slight.

Examine your polishing films, pads, papers... use a magnifying glass if you have to. Now, do you see any gummed-up paint residue on the polishing film? It will appear as a little roundish dot building up to a splotch on the polishing film/pad. If this is the case, the paint residue on your pad is probably your scratching culprit. Sometimes this buildup happens even with wet sanding while using a wetting agent such as a drop of dish soap. It pretty much signals that the aggregate media on the film is worn out - time to replace. (See Below **Bonus Tip - how to fix a good but slightly gummed up abrasive pad.) Next, after you are finished with all wet polishing, store the polishing kit in a baggie or container so it is not going to pick up contaminates while being stored. It sounds like there is some sort of contamination issue, just not sure where it is being introduced into your polishing process.

*Polishing Tip - Another hint taken from wet sanding more than a few full-sized cars is to use a dense foam pad to back up your sanding film / paper. I use the (3"X2"X3/8") McGuire's Black Foam pads that I cut down to size with a super sharp knife. I actually use a kitchen butcher knife to cut them, to get a straight square cut I take a piece of wood block a little longer than the pad set it on the pad and use it as a knife guide. The knife has to be really sharp to get a good smooth cut, the foam will tear otherwise. Then I use these Mini-Pads to back up the smaller sanding films and even the sanding pads while wet sanding / polishing. The foam pads control and distribute the pressure evenly across the pad. Use just enough pressure while polishing, so you feel just a slight drag, not a full-on cutting action like with sandpaper.

** Bonus Tip - You can maintain polishing films / pads with an art gum eraser, or the gum-rubber pads made for cleaning sanding disks, or to remove latex masking fluids (used by watercolor artists). Both the eraser and the cleaning pad can be found at a well-stocked art store, (or Dick Blick, Jerry's Artarama, Cheap Joe's websites). Both the eraser and cleaning pad are used just like an eraser on paper, best results are rubbing the eraser on the sanding pad in one direction until you get all of the embedded contaminants off of the pad. If you cannot get it 100% clean, then it's time to replace that pad / film.  This trick works to extend the life of sanding sticks and sandpaper on the bench as well.

I appreciate the detailed break down. Yeah I’ve had some previous paint built up on some of my pads that I would use on several bodies. Totally makes sense that the old residue would cause scratching on new projects. I’ve bought new pads and I’ll look into the products you mentioned.

[bobss396]

I find it too easy to blow through edges, etc using the thicker pads. They tend to wrap around things. I have a set somewhere... damned if I can find them.. which may be a good thing.

I have a couple of DM 9000 kits, one unopened. I buy odd cloths like 1000, 1500, 1800 and 2400 since they are not part of the kits. Again, I cut them in 4 equal-ish pieces and mark them on the back. If they start looking funky, I toss them. 

The 8,000-12,000 cloths load up fast, so I tend not to use them at all. I go to 6000 and use a polishing medium from there, 

[Skip]

16 hours ago, kymdlr said:

I appreciate the detailed break down. Yeah I’ve had some previous paint built up on some of my pads that I would use on several bodies. Totally makes sense that the old residue would cause scratching on new projects. I’ve bought new pads and I’ll look into the products you mentioned.

Recently retired Engineer, sometimes it helps to look at things from a "Process Analysis" approach, leads to detailed answers. LoL!!