When doors are off, do you guys sand jambs by hand or just scoth brite before epoxy and high build? I'm thinking on areas with no defects.

If it's original paint in the jambs and there are no defects then Scotchbrite is quite acceptable. Note that it then only needs a sealer, no high build, before final top coats.

Thanks. Sounds to me that it should be sanded anyway for best result?

You'll want to sand probably with 400 or 600 grit and then gray scuff pad after then sealer then your color. Actually I should clarify you will want to sand then scuff then blow with compressed air then tack then wax and grease then sealer then tack and then color. If you want to do the job right, anyway.

It's not recommended to only scuff before painting because if you simply paint over the existing finish you will end up with too much overall film build. It won't look right, at least to a trained eye. If this is a job you don't care about and the customer is stupid feel free to do what you like. If this is your personal vehicle or if an insurance adjustor will be looking it over or the customer is not stupid, do the job right.

Sand the existing finish at least through the clear and then do the steps as I laid them out.

Make sure absolutely sure that you sand/scuff EVENLY. What you do here, do there. It goes without saying everything you plan to paint should be dull but evenly dull, if that makes sense.

Don't trip on any burn throughs, but do make sure you shoot a coat of sealer on there before top coating.

To save time what most painters do is mix their paint and clear together and shoot one wet coat and call it a day. On jambs and say underneath a hood or trunklid you can get away with this. Just make sure that one coat covers. If you see primer showing through anywhere as some colors just don't cover well, shoot another light coat. One good wet coat should do it though, assuming you use the right color sealer.

Unless the final color will be black do not use black sealer, same goes for white never use white sealer unless the paint will be white.

Quick tip for jambs whether you mix the paint and clear or not tighten the fan pattern quite a bit and lower your air pressure a bit. You want coverage straight away, don't try to paint jambs like you would the outside of a door or something, it's not necessary and generally to be avoided.

No high build we aren't block sanding the door jambs. You might do this only if there was some bodywork done and you need to recreate some bodylines or something but that's a big job and what you are describing does not sound like a big job at least to me.

When you are sanding I am assuming you know how to sand properly. If you don't have any flexible blocks the right size you can use a squeegee the thin flexible black ones and get 400 or 600 grit the ones with the backing you peel off and stick the sandpaper onto the flat side of the squeegee to get the countours sanded just right. Will make your job much much easier.

By the way a coat of sealer means exactly that, a meaning one coat. Now, when I shoot my sealer what I like to do is shoot a piss coat and then immediately shoot a light to medium wet coat and that to me equals one coat. Sealer is awesome if you shoot like I do because the piss coat fills in sand scratches and the medium wet coat further fills in the sand scratches and lays out a nice smooth surface for the paint to bond to and orient itself. Sealer is a must. The common mistake I see people make shooting sealer is either they shoot it too wet and get runs or too dry and then your paint is landing on dry spray (keep in mind primer is just another form of paint, and dry spray is always to be avoided.) You tack after sealer to pick up as much dry spray as possible as there is always some but you definitely definitely do not want to spray sealer too dry and then top coat over it.

Dokus wrote:When doors are off, do you guys sand jambs by hand or just scoth brite before epoxy and high build? I'm thinking on areas with no defects.

Are you taking the outside down to bare metal?
Jay D.

Dokus wrote:Thanks. Sounds to me that it should be sanded anyway for best result?

Sure. But unless people have been dragging their boots or closing the door on a seat belt or manhandling a child seat across the paint then the jambs are probably going to be in pretty good shape. Factory paint in these areas tends to be a bit thin so, if you start sanding then you'll likely break through and need sealer and/or primer. If the surface is good then grey Scotchbrite is more than sufficient to achieve a mechanical bond, even better if you use a scuffing paste with it.

Methyl Mike wrote:You'll want to sand probably with 400 or 600 grit and then gray scuff pad after then sealer then your color. Actually I should clarify you will want to sand then scuff then blow with compressed air then tack then wax and grease then sealer then tack and then color. If you want to do the job right, anyway.

P400? Why, unless you're taking out imperfections? Even P600 is too coarse under a metallic and scratches will show.

Wash first and then Prepsol, before you start sanding - otherwise you'll be sanding the contaminants deeper into the surface. Don't forget to blow with each tacking process. Most of the newer sealers specify wet on wet application with no tacking or denibbing until after the first coat of base. OP should use the procedure outlined in the TDS for the product he's using.

It's not recommended to only scuff before painting because if you simply paint over the existing finish you will end up with too much overall film build. It won't look right, at least to a trained eye. If this is a job you don't care about and the customer is stupid feel free to do what you like. If this is your personal vehicle or if an insurance adjustor will be looking it over or the customer is not stupid, do the job right.

Not true. Scotchbrite was developed specifically to provide a suitably keyed surface for subsequent coats of paint. It's recommended by paint manufacturers as an acceptable substrate treatment.

As for film build, if the paint in the jambs is original factory then it's likely to be in the order of 100μm. Adding sealer (20μm), base (20μm) and clear (50-60μm) will take DFT to around 200μm which is well below the 300μm threshold that should not be recoated.

To save time what most painters do is mix their paint and clear together and shoot one wet coat and call it a day. On jambs and say underneath a hood or trunklid you can get away with this. Just make sure that one coat covers. If you see primer showing through anywhere as some colors just don't cover well, shoot another light coat. One good wet coat should do it though, assuming you use the right color sealer.

Garbage. Mixing base with clear, apart from potentially putting together incompatible solvents or water with solvent is just going to reduce the coverage. If you need 2 coats to get coverage then 1 coat of a reduced strength product is never going to work.

Unless the final color will be black do not use black sealer, same goes for white never use white sealer unless the paint will be white.

Rubbish. Use the correct shade of sealer or primer as recommended for the formula of the paint you're using. The paint colour is designed to go over a particular shade and if you vary from this then you'll either struggle to get coverage or the colour won't be true and therefore not match.

For example, I did the bonnet and roof on a Subaru Forester yesterday. Colour was a mid-blue metallic and the formula called for Value Shade 7 which is almost black. Result was a good match even though I'd painted edge to edge and not blended in to adjacent panels.

Quick tip for jambs whether you mix the paint and clear or not tighten the fan pattern quite a bit and lower your air pressure a bit. You want coverage straight away, don't try to paint jambs like you would the outside of a door or something, it's not necessary and generally to be avoided.

You do NOT want coverage in a single coat. This would require an overwet application with potential problems such as solvent pop or runs.

No high build we aren't block sanding the door jambs. You might do this only if there was some bodywork done and you need to recreate some bodylines or something but that's a big job and what you are describing does not sound like a big job at least to me.

When you are sanding I am assuming you know how to sand properly. If you don't have any flexible blocks the right size you can use a squeegee the thin flexible black ones and get 400 or 600 grit the ones with the backing you peel off and stick the sandpaper onto the flat side of the squeegee to get the countours sanded just right. Will make your job much much easier.

Well at least I can agree with most of this. Note my earlier comments about P400 or even P600 being too coarse as a prep for basecoat.

By the way a coat of sealer means exactly that, a meaning one coat. Now, when I shoot my sealer what I like to do is shoot a piss coat and then immediately shoot a light to medium wet coat and that to me equals one coat. Sealer is awesome if you shoot like I do because the piss coat fills in sand scratches and the medium wet coat further fills in the sand scratches and lays out a nice smooth surface for the paint to bond to and orient itself. Sealer is a must.

One coat means one coat, not 1.5 coats. Sealer is not a filler and should never be relied upon to rectify sanding scratches. Apply sealer as detailed in the TDS for that product.

The common mistake I see people make shooting sealer is either they shoot it too wet and get runs or too dry and then your paint is landing on dry spray (keep in mind primer is just another form of paint, and dry spray is always to be avoided.) You tack after sealer to pick up as much dry spray as possible as there is always some but you definitely definitely do not want to spray sealer too dry and then top coat over it.

See my earlier comments on correct application of sealer, following the specifications in the TDS.

VERY GOOD
Jay D.

NFT5 wrote:For example, I did the bonnet and roof on a Subaru Forester yesterday. Colour was a mid-blue metallic and the formula called for Value Shade 7 which is almost black. Result was a good match even though I'd painted edge to edge and not blended in to adjacent panels.

Just to follow on from what I said above, here is the car. That's off the gun, untouched and good to go while colour is about as good as you'd get given that one guard had been resprayed previously and I had to average the colour between the two.

Thanks. Upon further inspection I found that my damage free jabs where not so damage free but had peel and rust so I just sanded it all down. Very tedious work.

Weird, I didn't see the other post when I replied last. I fixed the peel and rust in normal fashion, sanded the jambs like the rest of the car up to p320 blocksand. Next up I plan to do 1-2 coats epoxy and 3 costs of primer. Continue sand 400 to 800 before standohyd base. I use mipa acrylic primer 4+1.

I have no plans on using sealer, just reprime areas if I burn through. I just paint on my spare time so I'm not sure but sealers does not seem to be commonly used in Sweden. Non of my suppliers sells sealers, only some primers that can be thinned to use as sealer.