Bicycle Mechanics - what temp to bake paint?
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11-02-06, 04:09 PM
I read some of the posts on painting.. since I'm leaning toward painting my frame myself.
One thing I didn't see mentioned was if anyone had ever baked that paint job.
So I was wondering; if I fashioned some sort of 'oven' which would hold the frame, does anyone have any idea what temperature and time might help a rattle can enamel paint job cure?
11-02-06, 04:53 PM
The paint projects I've done using automotive paint worked best when cured with halogen work lamps about a foot or two from the painted surface.
11-02-06, 05:23 PM
Well I've got halogen lamps. How long did you light 'em up for?
And was that spray can paint? Or did you use a spray gun?
Dr. Deltron would be a good member to send a PM to and ask. He's one of our local paint experts. :)
Depends on the paints makeup and where you live. VOC rules were tightened up considerable the past 2 years. VOC regulations vary from state to state and some, like Calif has stiffer VOC emissions than the national standard and formulas for many products have been changed.
That being said, a halogen lamp generates enough heat without the infrared lens attached to dry out the solvents in the paint. "Flash/cure time" usually takes about 15-45 minutes. BUT many spray can paints contain uncatalyzed enamel and may take longer to dry/bond completely (tack free), even when using a heat lamp. In the past, air cure times for spray can enamels could take as long as 6 months before one could wet sand and apply a clearcoat. Modern formulations may cure in as little as an hour.
It all depends on what you expect the final paint job to look like. I've seen some excellent spray can paint jobs and many really obvious ones. Most of the paint errors is from spraying another coat on before the previous coat is fully cured and the paint wrinkles. Many use the spray cans because it's cheaper, readily available locally, and they only want to protect whatever metal or composite from the elements. If you take your time and just spray on light coats of paint (about 12-15" away) in a cross hatch overlapping pattern, light wet sanding between coats, spray can painting can be a very cost effective way to paint your bike and look pretty good.
If you know somebody with an airbrush, you can buy an automotive grade paint, catalyst, reducer, etc etc and really have a professional looking paint job for a bit more money spent...you already have a heat lamp, your halogen work light. Can go to a local auto paint shop to buy smaller quantities if the larger auto paint supply stores don't have or carry pint or quart sized cans. Most, if not all automotive paints have recommendations for the ratio of paint to reducer for the temp and humidity you plan to spray at. Any overspray can be easily wet sanded out and polished out with a fine/finishing automotive polish. Some add/mix-in "Flex agent", but that may be overkill since most paints after curing will flex to a certain degree without cracking. Regular enamel paints can be used but need to be thinned out with reducer for the best final results...usually the automotive paint ratios are close enough to work and you need to gather that info.
Or consider powdercoating your frame. Eastwood sells a home powder coating system or take it to a powdercoating facility. After spraying your frame with powder, it only takes 20 minutes @350°-400° oven time (or less depending on the system and powders they are using...infrared systems only take a minute of two) before its done and you can start assembling your bike right away. At home curing of powder coating depends on how many lamps you have (for full coverage) or if you have to move the lamp after one section has "run out" or cured, but it takes about the same amount of time for each section. Typical pricing for powder coating a bike frame, including abrasive blasting/preping and de-gassing, is about $75.00 (Andrews Powder Coating in Chatworth, CA). The home deluxe kit, including powder colors of your choice costs about $130...less if it's on sale...just need a small airbrush compressor (or air tank) that puts out 5-10 psi. My friend bought a home powder coating system to paint her car's wheels and calipers with a more durable and better looking coating/paint/look, and everybody seemed to want to powder coat something...lol...so the cost can be split among users/friends and she now has a nice selection of powder colors at her home.
11-02-06, 07:19 PM
Thanks for the lead cuda2k. By the way, I was checkin' out your bikes. They're all pretty similar to the 1980 SR Semi Pro I bought last night. I'm stoked. It's the same make, model and color that I rode everywhere I went during trade school 26 years ago. Nice chromoly frame, shimano 600 components. A decent road bike in it's day, as well as now, if you're old enough to remember downtube shifters.
I looked at it this morning and she needs a little more TLC than I first thought. The hubs and rims are fine, but half the spokes are rusted enough that I think a rebuild is in order before I take her out. And the paint is beat up more than it looked in the pictures on Craig's List. But then isn't that always the case? I think I can wax alot of it out, but there's half a dozen spots where it's down to the metal... hence my paint quandary. The cheapest one color professional paint job I can find cost more than I paid for the bike to begin with.
11-02-06, 07:32 PM
Thanks for that info as well. You know if I can get the frame powdercoated for $75 I might go for that. I'm going to see if I can contact Andrews. It's a nice lugged steel frame. And if I could get the whole thing powdercoated I might be able to paint head tube inset a contrasting color later on.
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