Sanding nightmare

[Modeldude428]

I'm wondering if anyone has any way they can help me out I've never really did much when it came to Preparing the body of the car before painting never really got that much into it but lately I've been trying to do better and get better at it so I was watching a video not too long ago about sanding down the car using a marker finding the lines on the plastic that didn't need to be there so I did that I used 120 grit sandpaper and then use a polishing  stick  to try and buff out the scratch marks and then added a coat of Grey Tamiya primer one coat only but I can still see the scratch marks from using the Sandpaper I don't want to go any further until I figure out what to do is there anyone out there that can give me a hand if pictures are needed I can definitely send them need help ASAP

[Fat Brian]

You probably need to go back with something finer than 120 before the polishing stick. Since the primer is already on try some 1000 grit to smooth things out and shoot another thin coat of primer to check your work.

[Ace-Garageguy]

In the first place, 120 grit is WAY TOO COARSE. If someone on a video recommended that grit, he's an idiot.

NEVER use anything coarser than 180, and even that's too coarse unless you REALLY know what you're doing.

(In sandpaper, bigger numbers are FINER...and 400 is about as coarse as you really want to go on plastic)

All that said, you're pretty much screwed at this point.

The only way to get rid of the sanding scratches is going to be to sand with much finer paper, and possibly re-primer, then re-sand and re-prime as necessary.

Another problem that arises now is that all that sanding and primering will obliterate fine surface details.

In future, it's MUCH better to remove the mold parting-lines ("the lines on the plastic that didn't need to be there") VERY CAREFULLY with files and control where you let the scratches go.

When you remove parting lines with sandpaper, scratches spread all over the model, far away from what you're trying to correct, and you face the problem you now have.

And let this be a warning...MUCH of the "expert" advice posted on YouTube is just flat WRONG...about REAL cars as well as models...and everything else.

Edited February 13, 2018 by Ace-Garageguy

[Mr mopar]

Next time use a scotch bright super fine pad ,all you want to do is a light scuff of the plastic to give the primer something to grab onto .

 

Edited February 13, 2018 by Mr mopar

[Miatatom]

Bill is right, Quentin. The more layers of paint (primer, color, clear) that you put on the model, the more you lose detail. My method of preparing a body is to wash it in Dawn dishwashing soap and then scrub it with comet and a brush until the plastic doesn't shine. Clean up all the pin marks, mold lines and then make sure those places are smoothly sanded with at least 1000 grit sand paper. Then, you're ready to apply paint. Personally, I'm trying to eliminate the need for primers altogether. The paint I'm experimenting with is Createx Wicked colors. Works good so far.

[StevenGuthmiller]

I agree with Bill, especially on his point about advice.

You're much better off seeking advice from members of a forum like this, many of whom are real "experts" rather than the self proclaimed experts that you will find floating around on the net.

 

Steve

[slusher]

Some of the videos on you tube are the person who made the video opinion. Best advice is in my option here.

[Snake45]

Yup, Bill's right. I never use anything heavier than #320 and that only for coarse work. Removing mold lines is more like #400 or #600 work. 

[Mike999]

8 hours ago, Mr mopar said:

Next time use a scotch bright super fine pad ,all you want to do is a light scuff of the plastic to give the primer something to grab onto .

 

Scotch-Brite pads have a couple of other modeling uses:

1. In the Other Model Car Magazine this month, there's a tip about using them as masks to get random rust patches on a weathered paint job.  Slice off a very thin piece of the Scotch-Brite pad, hold it up or attach it to the model and shoot rust-colored paint thru it.  Haven't tried it yet, but plan to soon.

2. Here's a weird trick that worked so well it surprised me. I have a beater '78 Trans Am project going.  I had the AMT "Pro Shop" version bought cheap at a flea market. It's pre-painted glossy black with all the gold pin-striping already in place. So I wanted to dull down the black paint but leave most of the fancy gold decals alone.  Carefully rubbing the finish with a fine Scotch-Brite pad did exactly that. Now the paint looks nearly flat black but the gold decals are still there.  I did "chip" some of the gold intentionally; all that took was bearing down harder with the Scotch-Brite pad.

[Art Anderson]

2 hours ago, Snake45 said:

Yup, Bill's right. I never use anything heavier than #320 and that only for coarse work. Removing mold lines is more like #400 or #600 work. 

From the time I first got the stuff (in an AMT Styline kit w/AMT body putty) back in 1961,  400-grit Wet or Dry sandpaper has been my "go-to" for cleaning up mold parting lines, finishing off putty work.  Only occasionally have I had to use my extensive collection of needle files doing bodywork.  I sometimes will use 600-grit Wet or Dry sandpaper, depending on any perceived need.  I find that Duplicolor Sandable primer does a great job of filling the minute sand-scratches caused by 400-grit (of course, I decant this into my airbrush color jar, then airbrush on the primer).

ONLY on very rare occasions do I ever go coarser than 400-grit, and then nothing more coarse than 320 grit, after which I polish the areas affected with 400-grit.  Airbrushing the primer allows me to achieve a very thin coating of primer, which I do polish with 6000-grit Micromesh polishing cloths, wet with water, prior to painting with the finish color.

Art

[Jantrix]

I never use anything courser than the blue 220 grit sanding stick on a model body. You can get them at any beauty supply store in the nail care section. They are easy to cut into narrower strips. Makes sanding, worlds easier than using sand paper.

[Modeldude428]

Wow guys you are all awsome thanks so much I took a lot of you guys advice I picked up some  less violent sandpaper  sanded everything back down  it actually worked out really really well it's not perfect but I still have my detail lines and I do have a good base coat down so I really appreciate everybody  for the awesome help soon as I figure out how to post pictures I'd love to post the body to see what you guys think of how it looks now with the primer coat on it

17 hours ago, Ace-Garageguy said:

In the first place, 120 grit is WAY TOO COARSE. If someone on a video recommended that grit, he's an idiot.

NEVER use anything coarser than 180, and even that's too coarse unless you REALLY know what you're doing.

(In sandpaper, bigger numbers are FINER...and 400 is about as coarse as you really want to go on plastic)

All that said, you're pretty much screwed at this point.

The only way to get rid of the sanding scratches is going to be to sand with much finer paper, and possibly re-primer, then re-sand and re-prime as necessary.

Another problem that arises now is that all that sanding and primering will obliterate fine surface details.

In future, it's MUCH better to remove the mold parting-lines ("the lines on the plastic that didn't need to be there") VERY CAREFULLY with files and control where you let the scratches go.

When you remove parting lines with sandpaper, scratches spread all over the model, far away from what you're trying to correct, and you face the problem you now have.

And let this be a warning...MUCH of the "expert" advice posted on YouTube is just flat WRONG...about REAL cars as well as models...and everything else.

Thanks a lot for the awesome advice to be quite honest with you I don't know how I did it but I actually saved it I didn't realize what you were saying about the Sandpaper being too thick too much grit so I did use a much finer one and I use a trick that a friend of mine showed me how to use this razor in actually get the lines back which I did send it again and then sprayed it Here's the final results

[black2002ls]

If you still have some scars from sanding with the 120 grit, pick up some Bondo glazing putty. You can find it at Wal Mart in the automotive section. Spread a layer over the affected area, let it harden, and then hit it with 800 grit paper. Once you feel like you have it smooth, hit it with some 1000 grit and prime. Keep in mind, you can prime just the area that you worked on. This will help prevent losing any panel lines or cowl detail.

[Fat Brian]

To post pics you can drag and drop them once you click in the "reply to topic "box or click on the "click to choose files" button to manually select them. Once the picture has uploaded you hit the little plus sign on the lower left of the picture to add it to your comment.

 

I'm glad you were able to save it, a good way to think about it is that any scratch you put in the body you're going to have to get back out. Using the least aggressive paper that can do the job is a good way to save yourself work in the end. I strongly agree with Rob about the nail files, find yourself a Sally beauty supply or similar and invest in 10 or 15 dollars worth of nail files. I use the pink fine grit and blue medium grit the most but having a black coarse grit around comes in handy for removing a lot or material quickly. 

Edited February 13, 2018 by Fat Brian

[Pete J.]

I'm a little late to this party but will throw in a couple of tips from my experience.  I have a little differant approach.  I use Micromesh sanding sticks. http://micro-surface.com/index.php/products-by-type/nail-buffers/micro-mesh-nail-buffer.html You can get these from a lot of places like MicroMark, but this is link is to the manufacturer and you won't get them cheaper.   To start you could get a few three grit, and use it to figure out what works for you.  I would suggest the 2400/4000/12000 initially.  Once you find out what works then order single grits of each.  I only buy single grits anymore because the multigrits will have one wear out well befor the other and you wind up with a lot of half used sticks.

I use these first to take of parting lines and major imperfection and always use them wet.  I have a small spray bottle with 50/50 alcohol /distilled water.  The alcohol acts as a wetting agent/cleaner.  After the initial sanding, I dry the body and spray it with a very light coat of Tamiya white primer(gray if the model is molded in white plastic).  I then re-sand it.  This will bring up any defects no matter how small.  Small sink marks or scratches will pop right out.  Also any mold lines you may have missed or not eradicated completely will also pop out.  If this shows any defect that are really too deep then some filler is called for and a re-prime and sand.   Once you have it sanded down with the finest grit ,then you are ready for another light coat of primer to make the surface uniform and then your color.   Good luck.