Questions about Painting and Sanding, ( not actual DIY)

[kcokla]

Let me by first stating that, out of all the places on this forum i felt this was the most appropriate, however if mods feel the need to move it feel free.

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I've got a few questions in regards to painting and prepping, in particular rims,
and i know that there are a few DIY articles, but i know with more prep work, they could turn out much better, and in addition id like to learn about sanding in general.

so my questions are:
what are techniques to sanding?
what paper grit should i be using and when? what do the number grits actually mean?


im planning to spray rims, and im guessing ill have to clean, sand, clean again, primer, primer, maybe sand again ( what sand paper? etc,) then paint then sand then paint then sand, then clear coat then sand then clear coat.

reason for this belief is i want an excellently smooth finish, and a very very shiney clear coat at the end and more or less want it perfect.


thanks :)

[OMG.JAI xD]

Sanding is usually used to either remove paint or smooth out surfaces.

With removing paint you can simply sand it straight down, or bog it up first and level it.

With smoothing surfaces, this is used in conjuction with a primer and can only be done with wet sanding.
Wet sanding is basically getting a wet surface and getting the sandpaper wet using soapy water.

Smoothing surfaces you have to use high grit sand paper.

Grit is the rating of a sandpaper.
The lower, the rougher.
ie. 400 grit has better sanding characteristics but heavily removes what ever is being sanded.
1800grit lacks sanding characteristics, but has a very fine surface. Used mainly to level a surface or smooth it out.


Traditionally, you start with a low grit sandpaper 800-1000 to start your base.
Then clean. Dry. Spray primer. Dry. and wet sand using 1400 and repeating the process but moving up in grit of sandpaper. Until the desired surface is acheived.
Finish off with a clean spray of primer. And you have a surface where the paint will stick on to with nice coating.

The longer and more care you put into the work the better the end result.
IMO. If you have rims with the original colour The surface should already be smooth. So ensure its clean and just start sanding with very high grit sandpaper.
Remember. Wet sand.


=]

[kcokla]

ill be abit more clear to help with advice,

the rims im painting are stock, no paint on them at ALL,
however when im finished id like my clear coat to be shiney as and for the paint to be smooth and awsome !

ive been advised to simply clean with greese remover etc,
prime, and wet sand and prime and then paint and wet sand and paint and wet sand and paint and clear coat then wet sand andd clear coat then wet sand and clear coat.

all with very smooth sand paper /high grit,

anyone shed more light?

thanks for replies so far!

[GIPONU]

firstly, wats the color or ur stock rims? silver or polished/chrome? nothing will stick to polish/chrome.

if u want it to be SHINY AS! then u should get a really high quality clear coat.
more quality=more money.
at my workshop, we use sikkens autobase clearcoat, shiniest stuff i've come across. but for like 5L of that ur lookin at $$600 with hardener.

if it's fresh painted surface will be smooth. what u want is "flat" like how flat the paint settles. to get that without too much hassle, u can clear it the first time. then cut it back with P1200-P1500. anything higher doesnt give enuf grit to cut back the clear coat to make it flat.

then re-apply clearcoat. to get it "flat" u can add more reducer(make sure it is also a high quality reducer) mayb 15% reducer would get it flat. but the more reducer u add the more likely u will get runs or sags. the best option would be to paint ur surface flat, face looking directly up towards the sky.

sometimes i get my spray jobs really "flat" but i use a slow hardener with around 30% reducer. but u gotta be really patient with it.

&& "and then paint and wet sand and paint and wet sand and paint "
really.. u wont notice much of a difference if u add enough reducer into the paint or unless ur gonna bring out a magnify glass to check it out. its the reducer that helps it settle flat. and ur wet sanding each time to remove dust particle or fluff that is in the paint which might have come from the tack rag or environment. then u give a dust coat of paint to cover up the sanding marks. usually cut back with P1500

hope that helps.

[kcokla]

^^ indeed it helps alot, yet at the same time as complicated things!
slow hardener ... what does this do? i assime ill be mixing it with paint?
how would i do so if im using spray cans?
and reducer ? same question minus what does it do!

[GIPONU]

^^ indeed it helps alot, yet at the same time as complicated things!
slow hardener ... what does this do? i assime ill be mixing it with paint?
how would i do so if im using spray cans?
and reducer ? same question minus what does it do!

oh rite... ur using spray cans.. ummm
u dont need to take into account the Hardener and the Reducer if u use spray cans.

but honestly. dont use spray cans for ur top coat. which is gonna be your clear coat. spray can clear coats arent as shiny/smooth/adjustable as automotive 2pak paints.

u could go to automotive paint supliers and get wsome nice clear coat. cover everything in ur encloosed garage,put some water on the floor and spray it in there. u will need the clear coat, hardener and reducer then.
hardener is just a catalyst for paint. reducer is a low strenth but high quality thinner used for thinning paints so that it can flow more easily when sprayed