I've heard it recommended that you just rattlecan your first few practice frames, ride them around a bit, and cut them up. I'm wondering what is a good way to prep them for paint.
I've painted several bikes, one being the frame I built. I've always brought them to the sandblaster, given them a quick wipe down with thinner and then painted. I use a 2 part epoxy primary, base coat, and clear coat bought from Sherwin Williams and shot with an HVLP spray gun. Per frame, the cost of primer/paint/clear has worked out to be about $60. But the sandblasting has been running $40-50.
I figure for practice frames I can cut costs down by using a cheap rattlecan primer and single stage paint. But how do I prep the frame? There is so much residue and stuff that the sandblasting cleans off. Should I just do some rough cleanup with a wire brush on an angle grinder and then clean up with some steel wool and mineral oil? Or are there any particularly good chemicals for cleaning up the frame?
Re: How do you prep your practice frames for paint?
Roburrito- For your needs there isn't much that you need to do, assuming you're only looking for short term rust prevention and not great looks. If you have access to a sandblaster then you're ahead of a lot of others.
While time consuming it's a good idea to fully sand the frame by hand down to clean/shinny metal. this does a few things. It gets you in the habbit of looking at EVERY square inch and this will sometimes let you see something you missed or could do better. Second, it is part of the "putting in your time and paying your dues". You will tire of hand sanding and want to get better with your brazing and filing if you're doing your own sanding. Third, hand sanding reduces the need for sandblasting time. Only a dusting with the gun will be needed to final clean and etch the metal. If you're not going to sand blast then just hand sand really well. If paint is planned then you don't have to worry about the "grain" that sanding leaves. If clear coating (and that's a very short term finish) lots of care to line up the sanding to make all the surfaces look good will be needed. for paint I'd start with 80 grit for the initial finishing then go to 120 grit for the pre paint sanding.
I would try to reduce the time between the dusting sandblasting and the painting to insure the metal is not starting to rust. Appling a metal prep before priming is a good idea. Paint manufactures have these that are in their systems but common Navel Jelly is a good low cost alternitive. Your wiping the frame off with a thinner just before priming is good.
Never use an oil based anything on a frame trhat's about to be painted. The oil will make it's way into the nooks and threads, not fully clean off and migrate back onto the outsides when you're spraying. Not good for paint adheasion... This is why some builders won't chase threads or cut surfaces till after painting.
Rattle can paint is low cost and also cheap, if you know what I mean. It won't flow well, will be more likely to have drips, won't be as durable or nice looking as good paint. But it will protect the metal for long enough to ride the bike a few hundred miles and is easy to remove later for the good painting.
The last commit i'll make is that the paint job is what most will look at and this will make or break your reputation. The paint job is your calling card. Few people can look past the paint and have a feel for the actual construction quality.
Now it's time for real painters to chime in and speak the truth. Andy.
Re: How do you prep your practice frames for paint?
Andy is spot on with his comments. I don't have much to add, other than that you should prep your bikes the same whether rattle canning them or professionally painting them IMO. Its good practice (as in "best" practice, not practice practice....although its good for that also) and it will tell you a lot about your work and will make the bike look better and any paint job last longer. (You might be surprised what can be done with a rattle can) You don't need a blaster and there are many builders and some painters that don't use one. Wire wheels (or composite) on an electric or air drill work fairly well in the joint areas and tubes go fast by shoe shining them with Emory. I would avoid angle grinders and related wire wheels...most are too course and an angle grinder is too powerful....one bad move or catch and you can go through a tube in a heartbeat.
Also, again to re-iterate and emphasize what Andy said....when the time comes to start selling bikes, your paint can make or break you. A good paint job can make a poorly built bike look like a million bucks, but a bad paint job can make the most finely crafted frame look average at best.
Re: How do you prep your practice frames for paint?
I've rattlecanned all my 14 frames, and yes, they look just OK compared to a professional's paint or powdercoat but better than I'd expected for so cheap and easy. My thought was to not spend money on my first frames with a couple hundred dollar paint or powder if I'm not going to be that proud of the welding and brazing on the frames. Rattlecan is a viable option for the first x-number of frames IMO. It's $10-20 total depending on the quality and brand of rattlecan you use.
As for prep: I do a lot of what Andy recommended -- 80 grit emery the tubes, wire-wheel the braze-ons and other places that are hard to clean with the emery cloth, then use either Acetone or even rubbing alcohol to clean the dust residue left over. I've also tried the Duplicolor PW100 prep-wipe towelettes and they definitely get the frame pretty clean.
For paint process I recommend: (1) a few light coats of a grey automotive primer, (2) lay on several light coats of the rattlecan paint - Duplicolor Metal Specks is pretty sweet (see pic) and lays down a thicker coat than regular rattlecan, and (3) a acrylic clear coat once the paint dries for a day. This will do a little bit of protection for the paint. But honestly, unless you're really careful because the paint is so thin it's easily scratched. The metal specks stuff not as easily. Attachment 46185
Re: How do you prep your practice frames for paint?
Roburrito...here's a single stage PPG DCC that I just layed down...
race frame repair with LIMITED time...literally off the weld table and into the paint booth, 16 minutes to spray, 2 hours to bake, 20 minutes to chase/tap/face and out the door it went. As quick and dirty as you can get.
Re: How do you prep your practice frames for paint?
When I started out with repairs, I was offering customers a no-charge rattle can clear to protect from UV. I then bought a touch-up pistole from ebay for 30.- EUR and a 2K paint set consisting of 2 kg black, 2 kg white, 4 kg clear, hardener and thinner for 70.- EUR. The effort needed was about the same but the results were worlds better. If you have access to a suitable compressor then spend the extra couple of dollars and buy a gun. You can get small quantities of paint from you local car painter cheap. You will be much happier with the results.
Disclaimer: I don't paint entire frames. Only touch-up small areas with clear or at most a base of black or white. If I need the complete frame done or there are colors involved I go to my trusted painter, who does great work.
Likes: 
How do you prep your practice frames for paint?
Reply With Quote
Bookmarks