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Monday
Apr232018

My Paint Curing Oven

When I went to work for Masi at the end of 1980, I immediately found that the level of paint finish they achieved on their frames was at a far higher standard than I had previously seen.

I had painted my own frames in England for a number of years before coming to the US in 1979. I knew how to handle a paint gun.

What I had not been exposed to was applying multiple clear coats to the frame, then sanding the surface with wet and dry sandpaper, to an absolute overall smooth surface, before applying a final overall clear coat.

Masi had two essential pieces of equipment that were needed to achieve this level of paint finish. A totally enclosed dust free paint booth and a paint curing oven.

The paint booth was a scaled down automotive booth, with a large electric fan that exhausted through the roof of the building. Replaceable filters caught the paint over-spray, and on the air inlet side of the booth, were special “Sticky” filters that caught dust as the air came through. Both inlet and exhaust filters were replaced every month or so.

Masi’s paint curing oven was no doubt shipped over from Italy along with all the other specialist bicycle manufacturing equipment when the Masi facility opened sometime in the 1970s.

The Imron paint we used had a chemical hardener added to it, and so would air dry “dust-free” at room temperature in ten or fifteen minutes. However, in order for the paint to be hard enough to sand, it would take days, even weeks to cure. A paint curing oven was therefore essential to the process.

When I set up my own facility in 1982, I needed this same paint equipment if I was to produce paint work to this same high standard. The paint booth was no problem as these are made up of standard sheet steel panels that bolt together. One can order a paint booth in any size of configuration.

I ordered one from a company in nearby Los Angeles. It was 12 foot square, (3.63 m.)  and totally enclosed as previously described. It was divided into a 7 ft. (2.13 m.) room where the frames were sprayed, and a 5 ft. (1.52 m.) room where frames hung waiting to be painted, and where they also hung after painting, waiting to ‘flash off,’ and become dust free.

Air flowed from back to front through both these two sections, keeping overspray from the newly painted frames.

The Paint oven was a whole different matter. I doubt any such piece of equipment, specifically for bicycle frames, was even made in the US. However, I did find a used bakers oven that I figured I could adapt and make it work. It was about 7 ft. tall, 8 ft. wide, and about 4 ft. deep. (2.13 m. x 2.43 m. x 1.21 m.)

The front was enclosed except for a small door where the bread and cakes were put in, and taken out. It was made of sheet steel panels, insulated with glass-fiber in between. I cut the whole front off with a hammer and cold chisel.

Inside was a rotating conveyer that carried the baked goods around the over as they baked. I had to remove and discard all this, and make hooks to hang 10 frames and forks as I remember.

I constructed two doors that split in the center, using 3 inch angle iron for the frame, sheet steel outside and inside with fiber-glass insulation between. I made the heavy duty hinges, and a special cam operated bolt system, to hold the door closed tight against a heat proof sealing strip.

The oven had large electric heating elements in the bottom, and a control panel on one end.  The temperature this oven could attain far exceeded that needed to cure paint. I set the temperature at 250 degrees Fahrenheit (121 C.)  The oven would take about 15 minutes to reach 250 F. then would shut off automatically. It would then take another 30 minutes to cool down.

A 45 minute bake would cure the paint to a degree that would normally take weeks to air dry. Also I believe the reason the paint has held up so well, on some of my frames over 30 years old, the paint was hard and thoroughly cured when the left my shop.  Air dried paint usually chips in the first year when the paint is soft and vulnerable.

Above is the only picture I could find of the oven.

 

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Reader Comments (4)

Very informative, as usual. I am curious how you sanded around lugs, cable guides, etc. without sanding through the paint on the prominent edges. I also wonder how many current builders have invested in an oven. I suspect the economics of this level of paint work are unfavorable for most.

April 24, 2018 | Unregistered CommenterJon Blum

Interesting post Dave.

April 24, 2018 | Unregistered CommenterStephen McAteer

Jon,
How did I not sand through the color? Very carefully with very fine grit wet or dry. Making sure there is enough clear coat to sand before reaching the color coat. In areas over decals that needed sanding hard, I put as many as 8 clear coats and sanded with 250 grit, finishing off with 500 grit. Used with water so it did not scratch.
Dave

April 24, 2018 | Registered CommenterDave Moulton

I worked in the automotive paint business in the UK in the 1980's, and can say that Dave was certainly ahead of his time when compared to the refinishing of cars at the time. A minority of car painters were using 2-component paint (requiring an Isocyanate hardener), and even fewer were using an oven. Using a clearcoat was limited to a minority of metallic finishes, and no one was using it over a "solid" color. Hence the durability and lasting beauty of the paintwork on our bikes. Thanks Dave!

April 24, 2018 | Unregistered CommenterMartinW

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