Klass Kote Epoxy Paint - Tested By "Mr Scale" - Dave Platt
Subject: KLASS KOTE Epoxy Paint System Product Testing D Platt, AMA 975
Test Conditions: Temperature 74.1 deg. Humidity 41%.
The paint was subjected to a number of tests to determine its application to the hobby industry, and in particular to Radio Controlled aircraft, boat, and car models; also to other forms of aircraft model such as Free Flight and Control Line.
In preface, it must be remarked that this field is an especially demanding one requiring a paint to be robust in unusually difficult environments. The paint must also display friendly qualities in use by amateurs who, often without suitable equipment or painting experience, expect pleasing results.
TEST 1 - Spray Ability
- The test paints and primer were sprayed at the ratio of 1 part resin, 1 part catalyst, and 1 part thinner. Pressure was 35 psi, using an auto touch-up gun.
- The materials sprayed entirely satisfactorily, and it was noted that despite not being pre-filtered, they sprayed cleanly.
- Two panels of approx. 12" square were sprayed onto a well-cleaned glass tabletop. These were: a) primer, and b) black with satin catalyst.
TEST 2 - Cure Times
- The paint dried dust-free in a few minutes, the primer somewhat faster.
- After 2 hours, the paint would still hold a thumbprint, but the primer would not. At 5 hours, the paint would not hold a thumbprint.
- The paints were then allowed to cure for the full-recommended times of 24 hours.
TEST 3 - Bond
Due to the nature of model building, with its requirement very often for intricate paint jobs with successive overcoats of different colors, the usual method of masking using tapes puts a severe test on the bond of the paint to any substrate and to itself. Accordingly, the test was severe. This consisted of burnishing a strip of 2" wide masking tape to the surface of the paint, then ripping it up in a sudden jerk.
The first test, carried out purely for curiosity, was made after only 1/2 hour. Although the surface of the paint was matted, the paint did not lift. Further similar tests were made at intervals all the way to the fully-cured time, and at no point could the paint (or primer) be persuaded to lift off the glass.
TEST 4 - Sandability
The ability of a paint to be easily sandable when cured is, again, important to modelers where it may not be in other applications. The building of a beautiful finish requires the paint be sandable AND unaffected by future coats.
All testing, using sandpaper grits from 220 down to 400, showed this paint to be easy to sand, producing good dust without loading the paper. As expected, the primer could be sanded in a shorter time than the paint. The primer proved to be sandable in 8 hours, the paint in 12. The paint that was sprayed using the satin catalyst also showed shorter sandable times than that which used the gloss catalyst.
TEST 5 - Fuel Proofing
The chemicals typically used in the operation of engine-powered models are particularly harsh on paint. Oil, alcohol, and especially the nitro-paraffin’s (nitro methane, e.g.) will often break down paints almost immediately. Sometimes, so-called "fuel proof” paints (butyrate dope, for example) will resist these chemicals for a while, but eventually succumb. In some cases, the fuel causes the paint to become sticky; in other cases; the fuel buries under the paint and lifts it off the surface.
The test procedure here was to soak a towel in fuel and vigorously rub the paint. When no effect was noted on the paint using 5% nitro fuel, the fuel was allowed to sit for an hour on the paint and at its edge, and the test repeated. When the paint survived this test also, the same towel-rub test was made using straight 100% nitro methane. The paint was unaffected.
A further test was made out of curiosity to see if amyl nitrate, (used as an ignition improver in model diesel fuels, and known to be hard on some paints) would affect the paint but, as before, no breakdown was observed.
TEST 6 - Opacity
Due to the frequent use of color-on-colors used in model building projects, it is important that the paint have outstanding covering ability. As an example of poor performance in this respect, one can cite spray-cans. Because these cans require that the tip stay clean, the response is to diminish the solids and pigment quotient. The result is that the paint is semi-translucent and repeated coats are needed to render a solid color.
The test used here was to mask an area within the aforementioned satin panel, and spray white over the black. One foggy coat was allowed to tack for a few minutes, and then a wet coat applied. The white covered well. The opacity of the paint is considered excellent.