Bicycle Mechanics - painting tips
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08-08-05, 06:38 PM
so i have my frame primed now and in my makeshift oven i made from tinfoil and lamps. i am painting it tomorrow, and though i have read up on painting, i am looking for some last-minute tips
first off, due to my housing situation i am forced to paint out of doors, with the frame hanging from a tree by a coat hanger. i know this is a dust utopia here in southern california, so does anyone have anything that will help me keep dust off the frame as i am painting it?
second off, i am going to pick up a heat lamp tomorrow before i paint to better regulate the temperature in my oven. what temp. should i keep it at? i've heard 140 is good for enamel. any suggestions?
i am planning on doing 2 coats of color and one coat of clearcoat. how long should i let the color coat dry before adding the clear? should i sand the color before applying clear?
thanks so much for the information. i promise to soak it up like a sponge.
08-08-05, 09:40 PM
You will be better served if you can support a long 2x4 timber as your hanging beam. The tree will shake dust and leaves off almost invariably. What I did when I did outdoor painting is a pair of ladders and a beam between them. Position it away from as many things as you can(including roads). I had the advantage of having a flat concrete roof, which proved to be a very good place to bake it too.
Enamel paint will be baked well in temps as high as 350 deg. That is what I bake steel handlebars and forks in and it produces very good results. Good that you already plan to bake it. That makes a tremendous difference on durability, in the short term,(it will get hard eventually unbaked).
Handle the primed frame with latex gloves to avoid finger oils, then once it is hung, clean it with a solvent such as mineral spirits on a lint-free rag(old white t-shirts usually work.) followed by a tack-rag, which you can get at NAPA or any competent paint shop.
Follow as many directions as you can that are printed with the paints or on the cans you will be using, and wait a full day before moving it to the baking process, to avoid marring it. The longer you can leave it baking before assembling, the better(as hard as it can be to stand it, a week is good).
08-09-05, 03:55 PM
thanks for the response.
whats the reasoning behind waiting a day to bake the frame?
also, should i do the baking process after the clear or after the color?
it would be very hard to wait a week to spray clear then wait longer to assemble it
thanks for the help
08-09-05, 09:34 PM
The call for patience is mostly to avoid handling damage to the soft paint. Attempting to move it too early will have a chance of fingerprinting. Ideally you would want to bake while the coat is fairly wet, but it is not always feasible for handling. This is why many paint shops will have baking lights mounted in the paint rooms.
The clearcoat should be done within fairly close time to the color as long as the two coats are same base(ie. urethane-urethane, enamel-enamel). Baking together will have somewhat of a fuzing effect between the coats which is favorable. The only time you would not want to bake the clear with it would be when you have decals to go in between to be cleared over. It sounds like you do not, so not a concern.
The general rule of thumb is do not assemble the frame if you can still smell paint. As long as it is still gassing it is not full hard and installation of cables and housings will leave marks. That is the reason for the wait.
08-09-05, 10:54 PM
thanks again for the info.
its nighttime so in the morning i will do the clear. i have the handling pretty under control, as i am leaving chrome on the chainstays and can handle the masked off area there. it is baking now, and i will wait as long as it takes to get rid of that smell :) thanks again! so nice to have people like you here on the internet
08-10-05, 03:41 PM
ok so i got one more question. my clearcoat i got, dupli-color acrylic laqueur, says under its directions to not paint over air-dried enamel paints. the paint i used was krylon rust-tough enamel. it is dried. so i'm going to go look for another enamel? based clearcoat now, but if worst comes to worst, what would happen if i painted over the enamel with the acrylic clear? and should i be sanding the color before applying clear?
thanks for the answers
08-10-05, 07:38 PM
Ok, that is combining types. Enamel can be coated with laquer, provided the enamel is hardened sufficiently that it is no longer outgassing, as the fumes will interfere with the clearcoat. That will cause lifting bubbles and peeling. The other issue, depending on the agressiveness of the clearcoat, is that laquer clearcoats can soften non-laquer bases. The general principal is anything can go over laquer, but not the reverse.
Urethane clear, on the otherhand will go over anything since the solvent is non-agressive. It costs more than the other types but for that regard it is worry-free.
Plain enamel clear can go on top of any of them, with the caveat that it is not always the most durable. In this instance I would go with enamel if cost/applicability is an issue, as urethane requires a little more facility and attention. Plain enamel will bake together with the color coat and be satisfactory.
You bring up a good question about the inter-coat sanding. You do want to rough it up, but not with paper. Take a superfine 3M Scotchbrite(available from any body/paint supply house) and lightly buff off the gloss. You will be amazed at how much "orange peel" effect you will smooth out in the process. Be careful, however, since you are rubbing off the surface. It is easy to wear through it, resulting in more color needing to be applied. The surface must be de-glossed(flattened?;) )in order for the clear to bond propperly and appear to have depth. Clean the deglossed surface with a rag moistened with solvent(no pressure on it) to ensure no fingerprinting or dust. Let the solvent air out so you cannot smell it, then procede with the clear process.
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