Sanding

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didihno
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Sanding

Post by didihno »

I am doing my first few resin models and after some disasters with putty, I now need a tutorial on sanding.

Wet, dry, paper grades, I need it all.

Share your knowledge, oh great modelling collective.......
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Post by Lt. Z0mBe »

Get thee to Wal-Mart or whatever equivalent you have on the EMerald ISle. 3M makes a package of wet-dry in many grits that will float your boat and will handle 99-percent of your sanding needs. The package runs from 220 (coarse) through 520 (finer) grits.

Then, get thee to a craft store. Look for a polishing paper. It's a plastic-backed, fine-grit sanding film. Use this, IN CLEAN WATER ON A CLEAN MODEL after all sanding is done, and all lines are rescribed. This restores the plastic back to smooth - if that's what you want.

Get thee to the Pharmacy/Apothecary. Pick up a nail buffing kit. They're about $1.19US. The'yre basically a polishing system on a sanding stick for buffing fingernails. Again, when polishing, USE CLEAN WATER AND CLEAN PLASTIC. USe these kits, in the exact order specified on the package, for buffing clear parts after they've been sanded with other sandpaper. IT takes a while, but with some practice, you'll never fear sanding clear parts. :)

Toothpaste and plastic polish make great polishing compounds. Both are easily available from the grcery and the internet, respectively.

For filing work, inexpensive nail files can handle the majority of the work. Again, wet file. But, get yourself a nice set of jeweler's files.

I hope this helps.

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Post by tak5haka »

Halfords is a great source for wet/dry paper.
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Post by Treadhead »

I always find it helpful to use sanding film wrapped around a block of wood or plastic (anything with a smooth and hard surface) . It makes the job much easier.
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Post by Warped Speedster »

OK, now you have all the right stuff to do the job.

Next step:

You probably already know all this, but the best advice I can give someone about sanding plastic is >Go Slow<.

It always sands off faster than you think it's gonna, and always in the wrong places. It's so easy to ruin a project. Sand a tiny bit and then look at it, sand a little more and then look at it. Always have enough light to see where you are.

And always remember when sanding plastic (or resin) on a flat surface, that the narrow sections (edges) are gonna sand faster than the wider sections. It's very easy to forget that. So apply pressure on the piece accordingly.

For sanding fillers (any fillers): Wait a few days (or even weeks) after drying, to make sure they've done what their chemical composition is gonna do. Even Super Glue will shrink.

A lotta people hate it but I kinda enjoy the sanding stage of a project.
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Post by Treadhead »

Another note on sanding...

When using Squadron Green Putty or any kind of putty for that matter, I get putty pits. This even happens when I thin the stuff.

I use the putty as a 'base coat' just to fill the area that I want to sand. After allowing the putty to cure, I then use a thick coat of Mr. Surfacer 500 (painted over the puttied area). I wait until it has cured, then paint another thick swath across the area again.

When that is cured, sand as mentioned before.

I've used super glue and this works well too -- except you have to use some either zip-kicker or baking soda to speed up the cure, then sand before it gets too hard. If you are gonna go this route, I would suggest baking soda. Zip kicker works well if you apply it directly to the affected are with a q-tip. Spraying it from a bottle is not a good idea as the zip-kicker will softhen the plastic and make it brittle.
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Post by Chacal »

A trick I use is watching TV. Nothing too attention grabbing, just TV. Sand slowly and gently, without much pressure. The TV helps you take your time, so you don't rush the sanding to get it over with (you better heed to Warped's advice >Go Slow<). Check every now and then, keep going.

If you use too much strength, you'll scratch the plastic too deep and you'll have to sand more to get rid of the scratches.

After the shape is as you want, switch to a finer sandpaper/sanding film, then to a finer still, down to the finish you need. Remember: After the shape is done, you need to get a good surface for painting.

Wet sand always. The water removes the sanded dust away from the part so the sanding is even and more efficient. Wet sanding also helps the sandpaper last longer (if the sandpaper IS MADE FOR WET SANDING - if it isn't, you'll ruin it in minutes).

I use sanding film (by K&S). I bought a whole bunch (some 15 packets of the regular – 150, 280, 320, 400 and 600 grit – and 8 of the micro fine – for polishing) of it last time I was in the US (1995) and still have unopened packets. Wet sanding is a dream with those, and it keeps each sheet going for a LONG time.
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didihno
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Post by didihno »

Good stuff lads.

Explain wet sanding.
How wet is wet?
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Treadhead
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Post by Treadhead »

First thing is to make sure that you have the "wet or dry" kind of sandpaper. It should say this on the package. I go with the recommendations that others have echoed on brands -- all have worked well for me.

As far as how wet, I just take the sanding film and immerse it in water. When you sand, you'll notice a slurry developing. This is just a combination of the water and sanding dust. Wash this off periodically and re-wet the paper (sanding film) when it starts to dry out.

Practice this a bit on some scrap. I guarantee you'll get the hang of it in no time :)
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Post by TER-OR »

how wet is wet?

There's a great trick using a slab of marble tile, a large plastic tub and lots of water. The black wet-sanding paper is needed. Parts can be easily sanded underwater. This is almost necessary when doing vacuformed kits.
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didihno
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Post by didihno »

I'm off to try wet sanding for the first time, it should be fun.
The model is the 1:72 Cylon Raider. And what a little beauty it is too.

Thanks guys.
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Post by Neb »

TER-OR wrote:how wet is wet?
This is almost necessary when doing vacuformed kits.
Especially vacuformed kits! :D You can never have too much water. Plus it keeps the paper from loading up. :wink:

Also, buy a brand name paper. I've used them all the last 30 years (auto body work) and there is a distinct difference. The 3M stuff is decent---the Black and Decker stuff is ok but wears out very quickly.
Last edited by Neb on Fri Aug 04, 2006 12:27 pm, edited 1 time in total.
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Post by modelnutz »

From the "For what it's worth, works for me" Dept...........................
When I was still building guitars and wanted to get the best finish in the laquer............I would wet my sandpaper then rub it on a bar of soap. The soap reduces the friction and drag of the sandpaper as your sanding. Washes off the surface as well using clean water.
Helps keep from pressing down too hard as well.


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Post by Mr. Badwrench »

I wet sand in the kitchen sink, with a trickle of water running over the model. I agree about the 3M paper, it's the poo.
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Post by TREKKRIFFIC »

didihno wrote:I'm off to try wet sanding for the first time, it should be fun.
The model is the 1:72 Cylon Raider. And what a little beauty it is too.

Thanks guys.
I find that a little spit works great for wet sanding. Saliva is thicker than water and won't run off or dry out as fast. A little spit and polish should do the trick ! :?)
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Post by Neb »

TREKKRIFFIC wrote: I find that a little spit works great for wet sanding. Saliva is thicker than water and won't run off or dry out as fast. A little spit and polish should do the trick ! :?)
Unless you've just finished eating a mouthful of M&M's.... :yuck:

Sorry....I had too.... :mrgreen: :wink:
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Post by Zen-Builder »

I had good results using non-foaming shaving gel for wet-sanding.
didihno
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Post by didihno »

Well I wet sanded my heart out dipping in water (the paper and the kit) every now and then.

Certainly works a treat.
Why do some build ups say that they sprayed a base coat and then sanded again?

I'm basecoating (Priming) tonight.
I might try the acrylic Vallejo airbrush paint, or the rattlecan auto primer.
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Post by Mr. Badwrench »

Base coating a model then sanding will show off the low points, cracks and pits, etc.
I speak of the pompatous of plastic.
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