When we replaced the covering and repainted a glider we etched the aluminum metal surfaces after stripping the paint before repainting. I'm told this helps the paint stick to the surface.
The aluminum wings were stripped and repainted by someone else and I see that the paint has already started to come off leaving bare metal.
i've read about using vinegar just prior to painting brass locomotives. Would this prep & etch be better?
greg - Philadelphia & Reading / Reading
When building my On30 Diesel shunter some years ago, I used a self-ectching primer spray, which I just sprayed on after a through cleaning and degreasing of the loco body.
I use denatured alcohol to remove the rosin flux on brass, then wash it in TSP-substitute. Shot it with primer, then on to the finish coats and it holds up well. It can't hurt to etch metal for better adhesion, though.
Mike Lehman
Urbana, IL
When prepping metal to prime/paint, acetone can't be beaten. Of course, it has its problems...
It has been my impression -- and I am happy to be corrected -- that the vinegar bath idea for brass locomotives prior to painting dated from back when imported Japanese brass locomotives were "raw" brass. (Indeed back when hobby shops actually had brass engines sitting on display shelves waiting for buyers that sometimes never came or only bought years later, those engines could be very tarnished looking).
In the later years of Japanese brass, and I think just about always with Korean brass, the locomotives were in fact painted a brass color that not only prevented tarnish but functioned for many guys as their primer. Other guys stripped off the brass paint and started again with raw brass. They may also have used the vinegar bath idea at that stage of the process.
Dave Nelson
selectorWhen prepping metal to prime/paint, acetone can't be beaten.
my understanding is that the prep is not necessarily a solvent for cleaning the surface like acetone. Prep is used to pit the surface so that paint adheres better.
I think some kind of mild etching is way better than the abrasive grit sandblasting method.
I've seen HO brass models where it was obvious the "custom" painter got a little too carried away with the grit blasting and the fine details started to disappear (those models have an overall "sandy" look to them that is different from paint drying before it hits the model--I'm talking about when you view the model up close or with magnification). So for me personally, any method of mild acid etching (like vinegar) combined with a thorough rinse and a good primer is much better than grit blasting.
Whether the solution pictured above will etch a bit more or faster than vinegar I have no experience to say.
Respectfully submitted--
John Mock
Keep in mind that many, if not all recent brass models have been painted a brass colour to hide the soldered joints, and many are also given a clear overspray. Unless you're using a really strong etchant, it's unlikely to have much effect.
In many cases, that paint can serve as a primer. However, most of the brass I've painted needed to be modified prior to painting. In some cases, removal of the paint could be done in specific places to allow soldering of detail parts to the model, but other times, a few hours in lacquer thinner would strip it entirely. This was especially useful when the model required extensive re-working.
I painted mostly with Floquil, and usually first airbrushed the entire model with their Grey Primer, simply to make the locomotive and all the added detail parts the same colour. I've also used the same procedure with Floquil primer before painting with PollyScale or Scalecoat, although Scalecoat generally does not require primer when applied to metal.I have used vinegar to supposedly etch the Zamac castings for a locomotive kit, but didn't notice any difference in the way the paint adhered to it as compared to ones not so treated.
Wayne
Gregc, "Back in the Day," I painted and repainted imported Japanese brass HO models on a fairly regular basis. I always added details, so locos had to go in a bath of lacquer thinner--outdoors or in a well-ventilated area nowhere near an open flame!--a la MR's, and their author's, instructions. Of course, this was a few years before the makers started overspraying them, even with clear lacquer. I would recommend that you use lacquer thinner or some other paint remover, get it all off, and then pickle it in white vinegar to etch the brass.
That being said, I haven't yet painted any locos (I'm still months--years!) away from that point, but a few years ago, I did finally complete an scratchbuilt O scale model of a Milwaukee Road gondola-mounted snowplow from the late Paul Larson's construction article in the January, 1957, MR. It has a brass underframe and wedge type/spreader blade and wood body, and this was my first experience using acrylic, so I was interested to see how it was going to cover. The brass plow and underframe had sat around for 17 years, so I had cleaned it, off using cloth and an old toothbrush, with Barkeeper's Friend brand cleanser. (Works great on brass and copper, no matter how crusty it is, but it gives brass a sort of copper tinge to it, so I'm trying to think of another way to clean brass that I want to leave shiny [I model old-time stuff].) So, while I was brush-painting the gondola body and underframe, I daubed a brushful onto the back of the plow blade to see how it would cover.
I intended to airbrush the large areas of the plow blades and wedge, but I was interested to test the acrylic's staying power, so to speak. It surprised me by sticking tenaciously. So, would I bother etching a loco with vinegar? I think it might be worthwhile, even though acrylics seem to stick really well (anyone remember my comment, a while ago, about the boxcar red spots on my black poly dishpan?).
Deano
I have attended some brass painting clinics and witnessed firsthand why it is necessary to completely strip models prior to painting. If they are not completely stripped of all gold paint and/or lacquer prior to painting, the edges of any paint or lacquer deposits will clearly show through the finished paint job. If I'm paying somebody hundreds of dollars to properly disassemble, paint, letter, and reassemble a model, as I do pay and have paid, I expect that painter to completely remove all old lacquer and paint first. Others may choose differently, but to me, the difference between a high quality end product and all those lesser "custom" quality paint jobs is night and day. I simply won't touch anything in the "custom" paint category without having a painter lined up to strip it and redo it.
Also, the better professional painters (perhaps few remain) will also clean up excess or sloppy solder on the models prior to painting.
I personally would rather have less models with higher quality painting and finishing. Others will make different choices and that's perfectly ok. We all have to live within our means.
I'm also currently learning to appreciate leaving some models unpainted (as my favorite painters have passed away or are retired from active work)...I'm in the market for a new pro painter for brass steam power, if there's anybody looking for new clients. (Needs some experience with the more complicated, multi-color with polished cylinder head, etc. paint schemes).
John
I'm not a pro painter...
I have painted a number of brass (and other metal) engines using various techniques. I've used the vinegar etching technique and have found this to be unecessary if the piece is properly cleaned and primed. My favorite priming technique is actually a two-staged process: after the metal preparation (I will get back to this), I first apply a dilluted coat of shellac (50% dilluted) using a good quality paintbrush. This method appeared in one of L. Westcott's books, and the advice remains relevant in my experience. The coat is so thin that it does not leave any brush marks. When completely dry, I use ordinary auto primer as a second coat. This might be unecessary, but I do it to make sure I don't miss any spots. For the mobile parts, I prime using a paintbrush (I still have a bottle of Floquil's primer, which was top notch for metal...). When the prime coats are completely dry, I use my airbrush to apply acrylics. These days I've been experimenting different brands with varying results in terms of color, but that would be off topic. Anyway, the method has worked for me.
As for the metal preparation, I have left the original lacquer finish on one of my engines as it seemed to be in good shape. It seems that I made the right decision given the state of the paint job (5 years later and no problems yet despite some handling). For the others, I've stripped the old paint with baking soda using Badger's sandblaster. The soda does not appear to damage brass or other metals.
As for vinegar, I've had one nigthmare experience, which was entirely my fault. I dipped the model and left it sitting on the workbench overnight. The next day, I realized that it had oxidized some of the moving parts, that seized as a result of the exposure to vinegar. The problem here is that it was a shay, with tiny moving parts that I had to dismantle to get the parts moving again. No harm done, thank God. So I'm a bit shell-shocked about using that method again. But I guess the lesson here is to not let the vinegar sit on the model too long... Here is the happy victim...
Let us know what happens.
Simon