I see no tutorials or a good write-up about feathering. I've read some posts but there are nearly 78 pages of separate threads. Perhaps someone has some pointers.

Question:
Does the clear need to be cut to the base when feathering above the repair area?

I am concerned with applying a base over an area where there is clear, even when it's sanded for adhesion. Isn't there a greater chance of paint delamination when feathered directly over clear?

Scenario:
I would plastic and tape ~6-8 inches above the primed area.

Can you post a picture of what you are working on?

I like to feather the base coat and then clear the whole panel.

Some photos. I finished MP170 in early December.

Inner cab is going to be hit with ford blue acrylic rustoenamel, or left as is. Painting the cab pillars, rockers, fenders, and feather doors when they get reinstalled. The box is months down the road.

A lot depends on the materials your are using, the age and color of the paint you are trying to blend to as to whether you will be successful.

There is no one size fits all in this process, which is why you are not getting any responses.

Blending the color into the surrounding panels is one step but the clear coat is another.
Some guys will try to melt the new clear into the old using a solvent. My experience is that those types of repairs generally start to show before long.

If you look at the fender on this Miata you can see where they had once blended the clear:


This is why I prefer to clear the whole panel where the blend is made.

Great, that aligns with the advice I got from the local shop. I've been diving into videos and articles suggesting ways to blend the base coat with the existing paint, though I can't recall the specific grit of sandpaper they recommended.

The idea of using solvents for clear coat blending was new to me. I've read about lightly sanding the area but have forgotten the exact grit, possibly 600; I have it noted somewhere.

Regarding the fenders, my plan is to strip away as much of the clear coat as I can using 80 grit before applying an epoxy primer. I might leave the top four inches of the fender alone and blend from there. I'm debating whether to continue with MP170 or switch to Tamco. The local shop recommends Omni, citing never having had problems with it throughout his time in business, and he offers lifetime warranties, which speaks volumes about his confidence in the product. He's the second best shop in town.

I suppose rubbing compound and polishing the clear after full cure is another method of blending. Correct me if I'm wrong.

I used Omni once. There's a reason it's cheap.

Where you are spraying over the clear, if it is in good shape< you can use a grey Scotchbrite pad (800 grit) and scuff the surface until it's dull.

For areas where you are stripping 80 is good for bare metal prior to epoxy but if you are only stripping to base or existing primer, then 180 grit will work.

Thanks.

I'm being diverted from completing my truck project due to the demands of caring for a relative with stroke and dementia, finding them appropriate care, and sifting through months of notes to prepare a complaint about inadequate care to the state. It's a challenging and time-consuming process.

So the images above is 3 coats of MP170, rockers and inside cab. The inside cab is going to stay as is, and I'll be applying butyl mats after everything else is painted.

This is my original idea.

Metal,
MP170 (3x),
Bondo filler or Feather Fill G2 (2x),
Red/Maroon scuff pad or 320 to level out,
MP170 (2-3x)
600 grit,
Base,
600 grit,
Clear,
Wait a week and hand buff.

I've been reading up on Tamco HP770. I've also read that you used MP170 previously. The above steps is what I figured with Omni,Evercoat and bc,cc. I could be thinking this wrong, but is HP770 replacing Omni,Evercoat entirely? An epoxy, filler, and sealer? I am not a professional painter, so that doesn't make much sense to me.

With an engineering background I would expect a sealer epoxy (mp170, or similar) on the bottom (metal) to seal it from moisture -- obviously let it flash per the tds, then sand; then apply a bondo or polyester filler on top of that -- obviously let it flash per the tds, sand; then reapply the epoxy sealer (mp170, or similar) to avoid any moisture into the bondo/poly to cause any lifting -- wait flash time, sand; then apply base, sand; then clear. Perhaps I could skip the sanding part, and wait for the specified TDS flash requirements and spray the next coats wet on wet? Though I suspect I have to do some sanding with the filler?

Suggestions?

wet on wet is the typical way to use a sealer.
Jay D.

Reading through this thread the discussion seems to skip from one thing to another with no clear resolution to earlier questions.

Just so we're all on the same page....

Feathering is the process of sanding down the paint layer(s) so that the transition from the repair, at the level of the metal, to the top of the paint is sufficiently gradual that it can be neither felt nor seen. Obviously the distance over which the old paint is feathered depends on its thickness. Original factory paint may be only 70μm thick, so can be feathered over maybe only 10mm, but on an older vehicle which has had a few repairs and coats of paint the thickness (paint only, not filler) could be as high as 500μm so the distance over which it needs to be feathered is much greater, maybe as much as 200mm, or more. Where the old paint is thick the risk of the feathered edge being visible increases significantly, which is one of the reasons why taking the old paint off completely is usually the preferred method.

Looking at OP's photos, and in particular the first one of the guard, I can say that the feathering of the old paint around the repair area on the flared section is almost definitely not enough. Needs to be feathered more to be not visible. However, feathering on some of the smaller repairs does appear to be adequate.

Blending is the process of achieving a gradual transition between a freshly painted area and the original paint. Generally blending is done with the base or colour coat(s) so that the difference in the colour from new to old is not visible. The distance over which a blend is done varies considerably. With paint that is an excellent match and a painter who is well experienced a blend can be achieved over as little as 150-200mm, but usually I like to blend over a third to half the panel.

Clear coat blending is where the final clear coat is not extended over the whole panel, rather terminated mid-way and the edge melted in. Rarely successful on bigger panels like doors and bonnets/boots etc. but can be used when doing narrow panels like cant rails, sills and some bumpers. Usually a special solvent thinner is used to melt the edge of the new clear and then that is later buffed. For painters without significant experience this is not a recommended method - too much blending thinner and you'll get runs, too much buffing and you'll lift the new clear where it thins. Even done well, where the repair is not initially visible, it will eventually become so as the clear is at less than its design thickness and will fail over time. A cheap and nasty, "car yard" type repair that, in reality, takes almost the same time as doing it properly.

Now, addressing some of OP's questions....

xF100x wrote:Does the clear need to be cut to the base when feathering above the repair area?

I am concerned with applying a base over an area where there is clear, even when it's sanded for adhesion. Isn't there a greater chance of paint delamination when feathered directly over clear?

Simple answer to your first question is "No". Generally a repaired area will be primed and the primer will extend on to the original paint (clear or solid). Just about any paint will be able to achieve design adhesion over a substrate that is properly cleaned and sanded. For base or colour coats that sanding needs to be P800 wet or equivalent (P500 dry on a DA or grey Scotchbrite). As someone with an engineering background you would be able to appreciate that a surface sanded with a finer grit paper can actually have a greater surface area than one sanded with a coarser paper.

Your concern about delamination at the edges of the blend is valid. It's not something that causes a problem but the bigger issue is that, particularly with metallics and pearls, the flake doesn't lay down consistently around the drier edge. To solve this a technique known as "wet bed" is used. A full wet coat of clear base, extended beyond the planned new base coat or to the panel edge, is applied immediately before the base or colour coat. This has the thickness and wetness to achieve the required adhesion and any overspray just melts in to the wet surface. Metallics and pearls lay down consistently, achieving a much better blend.

xF100x wrote:-- wait flash time, sand; then apply base, sand;

No, never sand base coat unless it's to do a little repair (bug in paint, run, dirt nib) and then usually dust over the repair with more base. Base coat does not sand nicely - won't feather well so sanding, very gently with dry P1200-P1500 is usually the go.

xF100x wrote:Regarding the fenders, my plan is to strip away as much of the clear coat as I can using 80 grit before applying an epoxy primer. I might leave the top four inches of the fender alone and blend from there.

No, don't do that. Where you are going to put new base coat then sand with P800 wet. Where you will just be clearing over the existing clear then P1200-P1500 will give you sufficient adhesion but not scratching that will be visible through the clear.

No photos of your doors but just looking at that guard the damaged area extends up pretty high. I'd suggest that your chances of blending over a narrow area are fairly slim. If you had a body line you might be able to use advanced techniques like fly masking or loose back masking but it looks like they're not an option in this case.

I'm debating whether to continue with MP170 or switch to Tamco. The local shop recommends Omni, citing never having had problems with it throughout his time in business, and he offers lifetime warranties, which speaks volumes about his confidence in the product.

I can't comment about Tamco because it's not available here and I've never used it. The brand does have a great reputation though, particularly for customer service. Probably the best thing is to just give them a call.

As for "cheap" paints I think you have to acknowledge that there are two kinds. First the ones that are cheap because they use sub-standard components - don't use these. Then there are the "economy" lines put out by the major paint companies. Omni falls into this category. Still high quality ingredients but lower concentrations, especially of expensive tinters. Quality ingredients means that PPG can still back your distributor's warranty. Lower price, of course, but the offset is that you have to use a lot more to get the right effect or coverage. My paint system is Axalta and I have an Omni equivalent that I can mix. But it might need 4 coats to get coverage of some colours, compared to the premium product which only needs 1.5 coats. Even if the premium product is double the cost it's still better value that the economy one. Have a look at what paints the really big, high end shops use - almost every one I've ever seen has used the highest quality paint lines. Better colour matches, less coats so less time in the booth and less cost per vehicle.

One other thing to think about is that warranty claims are often denied when paint brands are mixed - whoever you're asking will blame the other guy. For critical jobs I stick with all products from the one manufacturer. I'm an accredited refinisher so if I do that, and document the process I can offer a lifetime warranty and know that Axalta will back me 100% on the product.

xF100x wrote:This is my original idea.

Metal,
MP170 (3x),
Bondo filler or Feather Fill G2 (2x),
Red/Maroon scuff pad or 320 to level out,
MP170 (2-3x)
600 grit,
Base,
600 grit,
Clear,
Wait a week and hand buff.

And these are my thoughts:

Metal, Get your repair as good as possible at this stage. Don't rely on subsequent coats of filler and paint to hide a substandard job (not that you suggested this).

MP170 (3x), I know it's too late but I can't see the point of putting on 3 coats of expensive epoxy when it's just going to be sanded off.

Bondo filler or Feather Fill G2 (2x),
Red/Maroon scuff pad or 320 to level out, Use a long, hard block for your initial sanding of filler and you can go as coarse as P80 to cut quickly and get it flat. Depends on the size and type of repair but I like P100 which is not quite as coarse but still cuts fast. Once you have it flat then another coat if you need to fill more or then go to a fine filler. Sand that at P180 then finish off with P240-P320 before your sealer. Leave the red/maroon Scotchbrite in its packaging.

MP170 (2-3x)
600 grit, Why 3 coats? As an engineer you would understand that more is not better. One of any given product's qualities is elasticity and when applied over a panel that flexes with movement and expands/contracts with temperature changes a thicker coating will probably have less elasticity than one at the design thickness. No elasticity = cracking and failure later. Note that the MP170 TDS specifies 2 coats, not 3.

A single closed coat of epoxy will seal and you can then apply the base, or primer, without sanding or scuffing, as long as you do so within the design re-coat time. Importantly, a single light coat is less likely to have peel that will transfer through to the base and subsequent clear. Recoat time varies from epoxy to epoxy, 24 hours to a week but commonly around 3 days. Refer to your TDS.

Primer You haven't included any provision for a build primer. If your repair is so good that it's not visible after the epoxy then, yes, you can go straight to base. But it won't be.

Base,
600 grit, No, as above do not sand base coat.

Clear,
Wait a week and hand buff. Yeah, good luck with the hand buffing after a week of curing. You'll probably have dirt nibs and maybe runs plus peel that you may want to reduce. Doing it by hand will not work - you'll need a machine to buff out the scratching left after you do what's required to the surface.

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Thank you for providing the details. This and other information will help in the next couple of weeks. Perfection isn't the goal, given it's a truck, I am aiming for a reasonably good repair and paint job to conceal the repairs made.