Cycling Adventurer: How To... Paint a bike frame

The Cycling Adventurer
How To...	Paint a Bike Frame — Step 4

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The complete strip-down

If the paintwork on a bike is in really poor condition, such that there is crazing or cracking, lots of chips from locks or leaning against post, or scratches from accidents, or corrosion, or it has multi-colours that have masking ridges where the additional has been applied over the base colour... then a full stripdown is required.

You might need to do it in stages, depending on the thickness and quality of the paint. For the simpler jobs, I use wet-and-dry paper, starting with a quite coarse grit of around 800.

If things look like getting tough, with several layers of paint, I resort to using ordinary paint remover in a gel form. Sellys Poly-Stripper is my favourite in Australia.

You won't need a large amount of the paint stripper, and I have found that applying it thickly doesn't really accelerate dissolution of the paint. Factory-applied bike paint is tough, and there can be clear coats to get through before the colour coat, and finally the primer.

I use a large artist's paintbrush to apply the remover because it doesn't slop stuff all over the place, and the bristles enable the paint remover to be pushed into tight spots such as around the bottom bracket junction of the seat and downtubes and the chainstays. It also gets the paint remove into the lugs. Use gloves when applying it, and read the instructions on the can.

You will need to leave the paint remover for an hour or two, then use the back of a knife (or the cutting edge of a blunt knife) to scrape off the gunk. I've found a knife is stiffer and gives me more control than, say, a flat painter's scraper. However, scrape lightly, rather than trying to force the issue. It is preferable to remove the gunk before the paint stripper has dried off... otherwise, you are simply stripping off dried, bubbled paint.

Scrape the residue off on sheets of newspaper rather than letting it drop on the floor or worksurface — paint stripper is not a pleasant thing to get on your shoes or to traipse around the floor coverings inside the house. And use rubber kitchen gloves to work with it.

The main frame of the tricycle, stripped to the bare metal and ready for spraying on of the primer coat.

As you scrape off each layer, apply another coat of remover, and finally you will be down to the bare metal, with just a bit of the original primer left. Don't worry too much about removing all the primer, but pay attention around the various welds and the little nooks and crannies of the lugs.

Use a pointed scraper, such as the sharp end of a drawing compass. If you don't get the paint out from these sharp corners, two things happen — they can harbour moisture under the new paint and encourage corrosion; and the build-up of paint takes away the "sharp" appearance of the lugwork when the paint job is finished.

Pay similar attentioon to any indentations that are put in the chainstays to accommodate wider tyres or the chainrings. Like most paint jobs, the fine detail is in the prep work.

When you are down to the metal, or one primer coat away, use wet-and-dry sandpaper of about 820 grit to lightly sand all the tubes. Pay attention to the corroded areas.

If the corrosion is extensive, you might have to reconsider the project, particularly if it is deep into the tubing, and if the tubing already is thin. Generally, bikes from the pre-1990s, except lightweight racers, had pretty tough, thick steel tube-sets.

If the corrosion or pitting is only on the surface of the metal, then a commercial converter/inhibitor for either steel or aluminium, depending on the material, can be applied. You may get away with just sanding it smooth.

Rub down again with 1200 grade wet and dry until you have a good smooth surface. It may look shiny, but with tiny scratches in it. That's OK, because one of the roles of the primer coats is to fill in those imperfections, and those tiny scratches help the primer to stick.

If you have pitted areas, now is the time to fill those. Bodyfiller is good, but there are epoxy-based household fillers that do just as well. Apply with a slight excess over the pitting, cure, then sand back to a smooth finish.

One of the difficult parts about this stage is that the metal will have all sorts of colours and reflections, and it is difficult to identify by sight any imperfections. Your fingers can help as you run them over the surface. But generally, the primer will help fill the indentations as you spray and sand back.

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