Regarding Paint on Old Machinery
Photo courtesy of John Burgoyne
Like most engine or tractor rebuilders, there comes that inevitable time when that freshly rebuilt piece of old machinery has to be painted, a task few of us are qualified for and even fewer enjoy doing! Having rebuilt engines and machine tools for over 40 years, I would like to share my experiences and observations with the readers of GEM.
Over the years, I have seen a lot of over-restored engines and tractors, usually with the use of modern automotive finishes. While such finishes are very durable, they tend to be far too glossy and simply look out of place. Early equipment was painted with conventional oil-based enamels, usually applied with a brush and smaller parts being dipped. One difficult decision usually involves which parts to paint and which to leave bare. Nuts, bolts and valve springs are a difficult decision, although I believe most original manufacturers tended to paint everything that didn’t move (and some that did!).
One interesting thing I have noticed is that most old equipment did not appear to use a primer.
I have tried most of the popular store brands of enamel, but early in the game I settled on Valspar, mainly because they offered most of the popular engine and tractor colors. At first I wasn’t too enthusiastic about Valspar because of its very slow drying time, but as time passed I began to realize that a slower drying paint was also tougher and more chip resistant than a fast-dry paint.
I always use a primer and I believe that using the same brand is probably best. The top coat needs to be applied reasonably quickly after the primer has been applied, usually within 24 hours, to ensure good bonding and adhesion. Many of us fall into the trap of using an aerosol spray can to prime smaller pieces to prevent them rusting while we wait for larger parts to be prepared. Big mistake!
Aerosol primers use a different solvent that generally makes them incompatible with an oil-based top coat, so good bonding will not occur. Again, use the same brand and type of primer as your top coat.
When applying paint, I prefer to use a good quality brush, which allows the user to apply the enamel at full strength. Rough castings certainly benefit from brush painting, a good finish accomplished by applying an extra coat of primer followed by some sanding prior to the top coat.
While I advocate using a brush, there are times when spray painting is necessary. Conventional air-type guns can be problematic. First, the paint must be thinned with solvent to spray. This requires multiple layers of very thin coats, which tend to run easily. Secondly, a thinned enamel produces an unbelievable amount of “fog” or overspray, which will paint your lungs and everything else in your shop area, meaning you must use some sort of breathing apparatus and work in a clean space. Another type of paint gun is the HVLP (high volume, low pressure), but quality commercial versions are expensive and unwieldy.
At a local store that sells Chinese tools and goods, I found what looked like a gravity feed paint gun that claimed to be HVLP for under $20, and I found this product to be very satisfactory. I was painting flywheels on my 6 hp Sharples, which are about 4 feet in diameter, a job that would have taken many hours with a brush, but was accomplished in about an hour without the need for multiple coats. It will spray paint without thinning and produces considerably less overspray, and the finish was quite satisfactory.
The last, and perhaps the most important piece of information that I want to pass on to our readers concerns the shelf life of oil-based paints. I have checked with several manufacturers, who have all confirmed that oil-based enamel has a shelf life of approximately two years. Cans are supposed to be date coded, but that code is often difficult to decipher. To make matters worse, most paint stores are not aware of shelf life issues and cannot interpret the coding.
I recently experienced a painting disaster involving out of date paint. I had an unopened quart can of primer that had been in my stock for at least five or six years. When I applied the primer it didn’t dry, so I “forced” it to dry by leaving it in the 100 degrees Fahrenheit Texas sunshine for several days. When the top coat was applied, I found that I had almost zero adhesion, although I’m sure it didn’t help that the top coat was also probably out of date. This fiasco occurred with a pair of very large flywheels that then required professional (read: expensive) sandblasting to remove all the bad paint. I was not a happy camper.
Back to the subject of Valspar industrial and agricultural paint, it has become difficult to find. I used to be able to buy it at Tractor Supply, but they no longer carry it. Lowe’s hardware stores are supposed to be the stocking distributor, but I find that they only carry the home improvement products. Occasionally, it can be found in smaller hardware stores, but shelf life becomes an issue. Maybe a reader can enlighten me on this subject. I would welcome any input on the subject of painting and I’m sure that GEM would publish any info that readers would like to submit.
Please send your questions and comments for Flywheel Forum to Gas Engine Magazine, 1503 SW 42nd St., Topeka, KS 66609-1265 or email firstname.lastname@example.org
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