Clear-coat question
 

For those of you who repaint your own bikes, what is your process for the final clear-coat stages? I’ll be using Spray Max 2-part clear-coat spray and am confident about getting it on the frame. But beyond that, is there still a lot if sanding, buffing, and polishing left to do? And do you also clear-coat the chrome areas on the frame (chainstays and lugs)? My previous experience is with nitrocellulose lacquer on guitars, but this is my first time with the 2-part stuff. Thanks!

Sorry if any of this is redundant based on prior experience you have. I'm also adding the extra bits for others who may be inspired by your post.

First of all, first thing you need to know is you need proper respiratory gear if using 2K, and you need to keep yourself covered, long sleeves is ideal. Use in a well ventilated area, that stuff is serious business and can cause permanent damage.

Second, you need to confirm the paint you're clearing over is compatible and read about the application window if your base color. Super critical to check the application window, most paints I've cleared over suggest applying the clear within 30 minutes of base coat application, OR you need to wait until 1-2 weeks of curing time before you can clear.

Finally, pre=spray prep. Using a suitable oil and residue prep with a lint-free towel is key.

I like to make sure my base/primer is smooth before shooting color, I'll shoot my color in multiple coats within the window instructions on the can, then shoot my clear if going on-shot. If I'm concerned about garbage like stray dust etc, or I notice the color isn't very smooth when laying it down, I'll wait the week or more for cure time per the can/clear instructions, then wet sand, solvent, then shoot clear.

One thing I've notice though, everyone has their thing. You don't need to go much farther than YouTube and search "paint with 2K clear" to see about 20 different methods, and some serious safety ignorance out of people.

EDIT - For full disclosure, the above is what I've used when I used to work on Motorcycles, what I've used on various around the house projects, and custom case mods for electronics. So, take with a grain of salt. There are some guys on here who have way more experience specifically with bikes, and I'm not that guy.

Last December, I had my son (who has equipment and is far better at it than I) paint two bicycles for me with automotive paint. One thing that I learned while shopping for the paint is that there are cons - as well as pros - to clearcoating. They are prone to scratching, and you will only make things worse if you try to undo the scratches using a rubbing or polishing compound. I didn't apply any decals to either of those two bicycles, and decided to not go the route of clearcoating. On the other hand, I did apply a 2K clear on a different bicycle that I painted.

You DEFINITELY need to follow the safety precautions. Even with a pretty serious respirator mask and applying it outdoors, the fumes were very strong, and I had to take micro-breaks to let the air clear as I was spraying.

...apart from the respirator mask advice, which I will not repeat ( have one rated for this stuff from the Home Depot, and I paint outdoors in the back yard), here is my experience with the Spraymaxx 2K clear glamour paint, which I have now used on maybe 7 -10 frames as the final step.

It seems to cover all paints equally well. I have used it over both enamel and lacquer, with equally impressive results. I've only been using it for maybe 5 yers now, so I can't speak to whether there might be some longer term problems with using it over lacquer...but thus far it has been a magnificent final finish both for looks and durability. You do have to make certain to mix it very well before you start spraying...the full two minutes of shaking and another two after puncturing the hardener compartment. The spray can and nozzle are pretty high quality, and if there is anything you need to watch out for, it is to get a good saturated coat on the surface of your bike tubing (without runs), or you will probably end up with a little orange peel in the final surface. Which is not all that bad, given that this is a clear, so orange peel is less noticeable.

I have never done any surface prep to the underlying color coats, other than to apply the decals before the final clear with Spraymaxx. One can seems to cover an average frame and fork nicely. There is some cautionary advice in the literature to apply it within a certain recoat window for the color coat...I think it's maybe 48 or 72 hours. But on my projects I have often gone longer than that because I like to let the color coats dry some before I apply the vinyl decals. When applied properly, the stuff goes on as a relatively thick paint layer. So I've never seen any point in trying to wet sand the undercoats smoother than they go on over the primer.

You do need to hit the thing with some kind of tack rag to get rid of any dust or surface lint a little before you do the final clear. And the can only has a useful pot life of about 24 hours. so I spray it all out in one go...fork first, then frame. Don't spray out the final few sloshes in the can as it goes empty, because there's some risk of losing the quality of the spray stream right at the end. I mask any polished chrome, and don't paint it with clear. I am fearful that there will be some adhesion problems down the road, and pealing clear coat is a problem I'd rather avoid.

Some examples:

https://cimg6.ibsrv.net/gimg/bikefor...55f35a34c9.jpg
https://cimg9.ibsrv.net/gimg/bikefor...839f44088e.jpg
https://cimg1.ibsrv.net/gimg/bikefor...3ddffdfed5.jpg

^^^the Lenton on the bottom was a project that had pretty good, old (1958) original paint and decals. I used the Spraymaxx as a compromise with the idea of preserving the old paint and decals (which were a little fragile), but still having a bike I could ride without worrying too much about it.

Curious, has top-coating over the old paint held-up pretty well over the years? I've seen people do similar on automotive repairs in cases where the original clearcoat isn't peeling and the paint isn't a single-stage, which a lot of the solid color paints pre-1980 seem to be. I'd read elsewhere you can't use Spraymax 2K over single-stage paints, but I've failed to fact-check fully.

Thanks! Exactly the sort of ideas I was hoping for. On the bike I’m doing, the base coat will have cured for quite a while, and I’m still trying to decide if I want to get repro decals. The color is non-original, but I’d still like to identify the frame. I also have started the process of smoothing out the base coat - 400/600/800/1200 grit sandpaper followed by rubbing and polishing compound. I’ll get a good respirator and wait for some warmer weather or maybe try to find a spray booth to use. I’ve also thought about buying a very cheap, used 4-6 person tent to use as a spray booth in my garage. Again, I appreciate the thorough advice.

I use automotive 2 component clear coat. I used to not like clear coat, however, I've changed my tune. I don't have any experience with the spray can 2K clear coat. There is no reason that it cannot be as good as the stuff that gets mixed and shot with a spray gun. I do use Dupicolor color paint on projects and have gotten good results.

Clean the frame, keep the dust down, wear a mask and a tip that I learned from a YouTube video, shoot in the morning. The bugs are lazy and they are not out of their beds yet.

You may want to practice on something first. Just to get the feel of the how fast you need to move and how wide a path you will cover.
I paint under a carport tent. So, the sides are open.

I've never had a problem clear coating over decals on the bikes that have been done. I wait a couple of days before the next coat. I never coat chrome. Final stage for me is a wax job.

...I just finished that one this year, so I can't speak to longevity. I do know that thus far it seems to be much less fragile than the original stuff. Only time will tell.

To do a proper paint job the base coat should be sealed with the clear within the "critical recoat time," typically 24 hours. Further, the base coat should not be sanded. Failing to follow these steps will affect the durability of the finish. Lastly, with catalyzed urethane paint you don't want to inhale too many fumes, even with a charcoal spray mask, thus painting outdoors with good ventilation is recommended. If you get a dust spec here and there sand it out and polish. That's better than breathing the fumes.

What kind of prep is necessary for using this stuff over "Patina"?

...depends on what you want to achieve. In the case of that Lenton, in the few spots that were rusted back near the dropouts, I used some Rustoleum rust converter/primer tha leaves the spot black and ready to accept paint. Anything loose orr peeling needs to come off, but otherwise it's pretty user friendly. Note that I am not using this stuff in accordance with the commonly accepted "recoat window" advice. I accept all that as probably the best way to achieve maximum advantage in your final result (in terms of toughness and durability). But there are some practical limitations when painting bicycles that get in the way. One of them is application of stickers, which is kind of an ifffy experience when your color coat is less than 24 hours old. Another is in using the stuff as a topcoat in an attempt to preserve original paint and decals.

I freely admit I'm using it in experiments, and my experiments are in contravention of the literature that comes from the manufacturer. But I'm thus far pleased with the results.

^^^I presume it goes without saying that you need to strip the frame of components, mask anything you don't want painted, and to clean off any wax or other coatings with mineral spirits or some other solvent suitable to the job that will not further damage your patina.

...having said all that, I would not use the stuff over patina. Patina under glass looks different from patina. The paint itself is expensive (20 bucks a can), and the hazards involved in spraying it have already been mentioned. Finally, it will be very much more difficult to remove if you tire of the patina and want to repaint the frame. I'm uncertain if there are chemical agents that will remove it, so you're stuck with mechanical methods.

I have mostly used it as a final step in complete repaints/rebadges. It's a lot of work. Patina preservation is not hat important to me. You just wax it and get more patina with use. :)

Sikkens 2 part. Actually covers flaws and blems in the color coat. Had someone bring me their pre-sprayed color coat done, with issues but was easily covered over smooth. Build it up with light coats, typically wait 30-45 min between coats, of which each coat gets a very light scuff of 320. Don't compare this to heavily sanding and gumming. Also, the product is very forgiving when you first see flashing on the complicated tubing. Best described as the flashing disappears or melts in. That's it. Cures fast.

Another that builds depth and with robust quality is from Gemini (better known for coating wood products). Like above, the two part urethane cures really fast, can actually lightly touch by hand in 15 minutes. Wicked catylist to not mess around with and certainly suggest using better breathing apparatus.

My apologies for bringing back a partial zombie-thread, but I think you folks can help me out.

In the next couple days I plan to paint a bike frame. All the materials are auto-paint grade (PPG). I had the color coats custom made and loaded into rattle cans.

The frame and fork are hand-stripped down to bare metal(steel).

Paint schedule:
1) Dewax-degrease spray
2) 2K primer (Spray Max)
3) Spray color coat #1 (fork, head tube, parts of the top & down tubes, Spray Max 368 2071)
4) Wait 5-6 hrs (suggested by paint desk guy)
5) Mask up parts of fork, top & down tube with auto grade fine-line tape(3M)
6) Spray color coat #2 (frame & over masked parts of color coat #1, Spray Max 368 2071)
7) Wait 2-3 minutes and pull off masking tape
8) Wait ????
9) Apply decals (dry application)
10) Spray 2K clear coat (Spray Max Glamour Coat)

The guy at the paint desk says the base coat needs to be clear coated within 24 hours.

Question 1) I'm not sure how long I have to wait to apply the decals over fresh paint (color coat #2). Any ideas/experience? If I have to wait 5-6 hours to mask off the first color coat and then another 5-6 hours to apply decals...and then do the clear coat, this will be a very long day, assuming the day doesn't go south with wind, humidity....(I'm painting outside)

Question #2) As a fallback option, I'm considering skipping the decal step and going straight to the clearcoat 30 minutes after I spray color coat #2. If I let the clear coat set up for a day or two (the tech data sheet says the 2K clear coat can be sanded and polished after 24 hours), can I apply the decals and then clear coat again? I'm guessing the cured clear coat will need to be wet sanded with 1000-1500 grit, wipe with tack solvent, and then sprayed?

thx..

I'm relaxing at a camp site after the 3rd week of teaching another frame building class. My student had literally no idea whatsoever how a frame was put together and English is his 2nd language. Fortunately his frame turned out beautifully. Determination can make up a lot for any lack of skills. And years of teaching experience helps. He'll stick around and we will paint it together next week. So answering this question is a little like getting called to go back in to the office for a couple of hours after you've left for the week. Because of that I'm not going to review all your steps but just provide some basic suggestions.

Let your primer set up as long as possible. Auto respray places want to move as quickly as possible through the whole process to make a profit so they are focused on as little as possiible time delays. I assume you can take your time. I usually put on 2 or 3 primer coats. I wet sand the primers with 600 grit paper. Then I apply the color casts. The House of Kolor paint I use requires putting clears over color coats without delay or that can weaken the bond between coats. The time between the color and clear depends on your paint choice. Now again I would let the clear have plenty of time to harden (I'm assuming you have activated clear that hardens by chemical action). These are your intermediate clears designed to protect your fragile color coats. You can speed up and improve this process by putting the frame in a car parked in the sun. Use courser sandpaper like 600 grit on your intermediate clears (at least 2 coats to prevent sand throughs) so the later final clear coats can bond better with the hardened clears. Now you can do whatever with decals without worries about time windows before putting on the final clears.

Polishing final clears is a whole other chapter.

...first, I am not nearly as fastidious as Mr Fattic. It's just not in my nature. :o

Second, and more importantly, I have already said up thread that I routinely go outside the manufacturers recommendations about recoat windows. Thus far, this has worked out OK for me. But the timing off sticker or decal installation is a major sticking point in painting a bicycle, as opposed to a car (which are usually graphics free.) When the Urethane clears first came out, all the car guys were oohing and ahhing about how cool it was to have this clear, high gloss finish coat that would go on over almost anything, create a durable final surface, and I still feel that way.

It is true that you can put some sort of intermediate clear coat over your more fragile color coat within the window. Then wait for it to dry (it sets up pretty rapidly to where you can work in the stickers.) But I remain unconvinced that this makes for a better overall result. The issue with applying the decals to a color coat that has not had time to fully bond and harden (it never gets really hard unless you use an epoxy paint as your color coat, and this is rarely done), is, off course, that in positioning and repositioning the vinyl graphics, some of it will lift. Which makes the job still salvageable, but a lot more time consuming to fix.

Take it for what it is worth, since I am satisfied with somewhat lesser results (I don't set up a spray booth, and I paint in the back yard, in the shade of a tree). But I prefer to simply let the color coat cure for a couple of days before I go at it. The only way I can get the graphics on there straight is with the use off some low tack masking tape boundaries, on which I have inked some alignment lines. Even the low tack stuff needs to be toned down a little, by sticking it on your shirt or a rag to make the adhesive less aggressive. Otherwise I risk lifting some of the color. And I'm too slow at this to get the graphics positioned rightly without those guides and some measuring while in process.

I have not, to date, noticed any tendency toward early failure of my paint jobs, even though done in this manner. I wish I had the time and patience (and money), to mix and apply intermediate clear coats, but I don't. I do have a policy of doing fill color in any pantographing and any lug lining after the final clear coat is already on and cured, for this very reason. I often make small errors on that stuff, and it's easier to remove it and fix it once you have the clear urethane on and hardened. I've been doing frames this way at a rate off four or five annually for about six or seven years now, so it's a small sample size.

On getting a good result from your final application of clear urethane: Buy and use the stuff called "Clear Glamour". It is formulated to go on and hold a little bit thicker than some of the other clear urethane formulations. And take an old piece of pipe or round conduit, and use it to practice applying the paint so it is covers the surface all around to a point just short of running. It's hard to describe, but the surface gets a wet look, and what is happening is that the paint layer is on there in sufficient quantity that it levels itself, creating a surface that will look glassy as the final result. Done correctly, it requires no polishing to look good.

If you do get a couple of runs, don't attempt to fix them, other than to rotate the frame to reverse its direction, so they won't continue. I paint with the frame held from an old seat post of the proper diameter, inserted far enough to hold securely. That post is secured in a standard bicycle work stand clamp, masked with old socks. So I can spin the frame I'm painting in any orientation I need to work on any aspect of it. Saves my aging body from awkward positioning.

Any small runs will eventually dry clear, like the rest of the paint. You can polish them out if they bother you, but it's a lot of work. Otherwise, with multiple light coats of clear urethane, there's some risk of a less glossy surface in the final result, or even the dreaded orange peel. :) Try to relax, and be grateful it's just a bicycle. I hope this is of value to you. If nothing else, as a primer on how the less fastidious do it. You can choose your personal standard of perfection.

Fwiw
 

https://cimg4.ibsrv.net/gimg/bikefor...16b7d483ed.jpg
https://cimg6.ibsrv.net/gimg/bikefor...92bf720db4.jpg
https://cimg7.ibsrv.net/gimg/bikefor...6fa4a4e523.jpg

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...and don't try to do it all in one day. A reasonable schedule for me is to get through a couple of primer coats, and a color coat one day, let it hang from the roof gutter in the back yard for a couple of days. Then apply the vinyl graphics, wait a day for the water to fully evaporate from the wet method application and for the adhesive to cure. Then do the final clear the following day. Might take longer if there are some color bands or it's a two color paint scheme. These are not full days, just a couple of hours at a time each day.

I use disposable cups on my clear coat only spray gun. After I finish, I'll leave whatever is left in the cup undisturbed. It can take a full month for the liquid to shrink to its final solid size. Even after a week it has only shrunk a third of its final size. This depends on weather conditions of course. The process can be speeded up or slowed down depending on the ratios of activator and reducer involved. I don't want a fast drying clear or I am more likly to get the dreaded overspray (a dulling) or orange peal (where the paint doesn't flow out smooth because it is hardening up too fast).

House of Kolor paint was formulated by a custom car painter wanting to do glamor candy and pearl paint jobs. His last name started with a K and that is why they spell Kolor with a K to promote their brand. It eventually got bought out by Valspar paints. Over the years their formulas have changed. I got started using it 35 or so years ago to get more eye popping results than I could with Dupont Imron. One of its problems for covering bicycle frames by some professionals was that the paint would separate between layers when it was hit. The reason for the separation was that those painters did not keep within the recommended time windows between coats. It was more efficient when doing several frames at a time to wait longer so more frames would be ready for the clears (or whatever came next). I was always very strict about staying within the recommended time windows so that I didn't have unhappy customers. And I never had trouble with paint separation. My experience is entirely with H of K paint and I have no knowledge if other kind of paint is more forgiving.

I also almost always spray a sealer coat between the primer and color coats. This serves multiple purposes but most importantly creates better adhesion. This would be too much bother and expense for a hobby painter. I love H of K primers because they work well and come in primary colors (red, yellow, blue as well as white and black) so they can be mixed so the primer color is similar to the top coat colors. I've converted a few of my fellow pros to using those primers because of its advantages. These primers could work very well for hobbyists too. In fact their primer colors are so good they can be used as a color coat.

This is a bike I made and painted for myself using only H of K primer colors including the yellow and blue decals. They are painted on. I put an additive in the clear to create the matte finish. I made the frame in one of my framebuilding classes as an example to students to show them how to braze.
https://cimg0.ibsrv.net/gimg/bikefor...1a5de4db0.jpeg

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...here is a link to the manufacturer's data sheet for Spraymax Clear Glamour.

I have pretty much taken this as a carte blanche for experimentation, and have, thus far, not been disappointed. I'm familiar enough with a couple of different paint systems to know that you will get a more cohesive overall finish staying within some reasonable recoat windows. As already stated, I find the application of vinyl graphics to be a limitation in this regard. I might be more relaxed about this because I'm only doing it for myself, and I won't complain.