Synthetic and enamel paint explained

[CHARLES lipscombeParticipant @charleslipscombe16059]

S.O.D.

You are right on the money regarding the term Enamel, we would all be better off if this term was consigned to oblivion. Historically, the alkyd paints were so far in front of anything else when they appeared that the term enamel was not an unreasonable comparison.

Complicated? I think it all depends on your background, the other man’s technology often appears that way to the outsider. After a lifetime working as a chemist on the resins used to make paint it seems easy to me! But I really struggle with some of the articles in MEW and anything electronic baffles me completely.

Paint technology suffers from two extra complications not found in engineering i.e. meaningless terms like enamel and coach paint, and tradition.

Painting is a hot-bed of traditional ideas, often against all logic. Why would anyone would want to paint something in cellulose paint when modern paints are better in every conceivable way? Presumably because their vehicles were originally painted in cellulose and they want an original-looking finish? Modern finishes are visually indistinguishable from a first-class job in cellulose and if you can't see the difference,what is the point?

I have been retired (gratefully) for 20 years now so I am not up to date with the very latest, especially in Europe (I live in Australia). It was interesting to me that with all the fire/explosive problems of cellulose paints, they were eventually banned on emission grounds. Especially so because the acrylics use similar solvents.

Nick Clarke.

Yes always go to a specialist or risk disappointment later. Also be careful to use products from one brand. If you use one brand of paint and someone else’s thinner for example, you are giving the paint manufacturer an automatic get-out clause if anything goes wrong.

Andy Carlsen

Yes there are many different acrylics (and alkyds, and polyurethanes, and polyesters) and to me it is debatable whether for a layman it is worth acquiring more than a basic knowledge. It is enough to know that acrylics are generally excellent but normally affected by petrol while polyurethanes are just as good or better than acrylics and not affected.

Generally:

I have yet to see a water-based finish that would be suitable for the kind of items that we make.

Becoming popular in Australia amongst hobbyists for high temperature situations is Brake Caliper Paint . This requires mild stoving conditions but is high gloss, durable and as tough as old boots. It is one-pack and I would guess is a polyurethane.

Chas

[Nick Clarke 3Participant @nickclarke3]

Posted by CHARLES lipscombe on 30/05/2020 09:51:54:

Painting is a hot-bed of traditional ideas, often against all logic. Why would anyone would want to paint something in cellulose paint when modern paints are better in every conceivable way?

It was interesting to me that with all the fire/explosive problems of cellulose paints, they were eventually banned on emission grounds. Especially so because the acrylics use similar solvents.

Cellulose is far easier for the amateur to spray – runs are far easier to avoid and if you did get a run in a synthetic it was time consuming to repair due to the paint being softer for longer, although since the advent of modern de-nibbing files less so. Also, when I worked in that field, Cellulose was appreciably cheaper to buy then although, even including hardeners, there is not much difference today.

Regarding the fire v. emission issue – 45 years ago the one-man spray shop was common and as these almost exclusively used cellulose many would have little in the way of extraction or air filtering. There was less of a risk of fire etc as the solvents went out into the atmosphere and became an emissions problem. Put in a spray booth and filtering to retain the solvent vapours and you have a greater fire risk, but fewer issues with pollution.

[CHARLES lipscombeParticipant @charleslipscombe16059]

I'm not sure about the ease of application issue. I am currently using an acrylic paint which is sooooo easy to spray and avoid runs. The trick with acrylics in my experience is to put them on "so wet it frightens you" to avoid orange peel. In my case the paint colour is black which in all paint systems is usually the most troublesome colour to spray. This is because the carbon pigment which is almost universally used in black paints, affects flow of the paint in a way that promotes runs.

Why do I use acrylic? I am painting replica bulb horns (think Laurel & Hardy and model T fords). The product is unlikely to have contact with solvent e.g. petrol , drying to the dust and insect proof stage takes about 2 minutes and I get a gloss finish. What's not to like? It's the usual story of horses for courses.

Chas

[Clive Brown 1Participant @clivebrown1]

In the book "How (not) to Paint a Locomotive", by C. Vine there's a chapter giving a resume of paints of dfferent types which might be of interest to model engineers. The book as a whole is an interesting read although rather a counsel of perfection for us ordinary mortals.

[Nick Clarke 3Participant @nickclarke3]

Posted by CHARLES lipscombe on 30/05/2020 13:07:46:

I'm not sure about the ease of application issue. I am currently using an acrylic paint which is sooooo easy to spray and avoid runs. The trick with acrylics in my experience is to put them on "so wet it frightens you" to avoid orange peel. In my case the paint colour is black which in all paint systems is usually the most troublesome colour to spray. This is because the carbon pigment which is almost universally used in black paints, affects flow of the paint in a way that promotes runs.

Why do I use acrylic? I am painting replica bulb horns (think Laurel & Hardy and model T fords). The product is unlikely to have contact with solvent e.g. petrol , drying to the dust and insect proof stage takes about 2 minutes and I get a gloss finish. What's not to like? It's the usual story of horses for courses.

Chas

I used to have to troubleshoot issues refinishers had with our products which sometimes involved demonstrations. But I doubt I could even set up a gun nowadays – it was a very long time ago, but you spray a small tubular object in black of all colours and lay it on wet-on-wet – Sorry friend, but I am not worthy!! You are better that I ever was at getting the paint on, not then, let alone now! Cars are easy in comparison.

Take care,

Nick

[Tim StevensParticipant @timstevens64731]

Charles Lipscome has not come across baffling engineering terms? How about 'Imperial' spanners which don't fit the bolts which built the empire, but only those from the USA or post war (and so post empire). And I invite him to consider the brushes in electric motors and the points which used to be used in ignition systyms. Every trade and every profession has them – its partly to keep beginners and outsiders in their place, of course.

Grumpy as usual – Tim

[Nick WheelerParticipant @nickwheeler]

I agree with Charles, in that 2k is much more forgiving to paint than cellulose. It needs fewer coats(2 gives a good finish) which reduces the chances of screw-ups, it uses much less solvent which further reduces screw-ups, you need less paint so the small increase in cost per litre over cellulose is actually a gain, and the gun finish is better, longer lasting, more durable and not affected by common chemicals like brake fluid or fuel. Then there's the time taken; a fast acitvator on a warm day will have the second coat ready to unmask by the time you've cleaned the gun, tidied up and made a coffee. This is even more true of 2k high build filler, which is fabulous stuff; two coats applied over metal and filler with a roller can be flatted within a couple of hours. You can go from bare metal to finished colour the same day!

It's good on engine blocks, cylinder heads, brake calipers and just about any surface in the workshop you might want to paint. Last week I brush painted with 2k the windmill weathervane my Dad made from hardwood scraps – the base made from mahogany windowboard doesn't show any grain, even with no primer.

You do need to be a bit more careful with PPE, but anyone who sprays cellulose without overalls and a decent filter mask is an idiot. My air fed mask cost £100, but it does make compressor selection more critical.

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