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Painting! There one day, gone the next!

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Ian Johnson 109/11/2019 01:04:16
174 forum posts
50 photos

I've been building the Stothert & Pitt beam engine for what seems like an eternity! And despite putting it off for ages, the time has now finally come to painting it. I like green by the way.

So I got out the trusty Aerograph, filled the pot with green acrylic gloss. The unlucky base, beam, bearing stand and top plate was duly sprayed, and bingo! nuclear pea green! complete with runs and blotchy finish! That was Wednesday (see nuclear pea green photo).

20191106_205053.jpg

After about three seconds of deep thought I came to the conclusion it had to be destroyed, so the very next day all the bits were immersed in a bath of Acetone, the paint melted off.

20191107_201228.jpg

I'll start again with gloss or satin enamel, with a slightly nicer shade of green, probably sprout colour or runner bean maybe! And practice my airbrushing skills too!

Ian

John Penfold09/11/2019 07:43:27
23 forum posts
3 photos

Oh dear, lots more practice - or use a brush frown

J

JasonB09/11/2019 08:02:17
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16530 forum posts
1759 photos
1 articles

Build it up in thinner layers, with acrylics it can also help to warm the part beforehand to speed up initial tack so stand on a radiator for an hour or so before you spray it.

Largest nozzle/needle you have so paint does not have to be thinned excessively. Use an acrylic thinner rather than water which will dry faster between coats.

Also can't see if you have primed it or not, for a Kermit green like that a white primer will give best results and need the least thickness of topcoat to give solid colour, grey for a darker green.

Mick B109/11/2019 09:16:06
1241 forum posts
70 photos

Have to respect your colour sense. You know there are people who'd've left it that colour without batting an eyelid?

surprisewink

Derek Lane09/11/2019 10:10:13
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236 forum posts
56 photos
Posted by JasonB on 09/11/2019 08:02:17:

Build it up in thinner layers, with acrylics it can also help to warm the part beforehand to speed up initial tack so stand on a radiator for an hour or so before you spray it.

Largest nozzle/needle you have so paint does not have to be thinned excessively. Use an acrylic thinner rather than water which will dry faster between coats.

Also can't see if you have primed it or not, for a Kermit green like that a white primer will give best results and need the least thickness of topcoat to give solid colour, grey for a darker green.

Not only will the correct thinner/reducer help but it also does not thin the paint to be more transparent rather than opaque like water will.

Air pressure also helps with getting the coverage correct as well as control of the dual-action of the brush(it looks like a dual-action without looking it up).

They need practice

Edited By Derek Lane on 09/11/2019 10:12:37

Ian Johnson 109/11/2019 10:47:04
174 forum posts
50 photos

Some good advice here. Thin coats are good. I did thin it down with Acrylic thinner, and maybe I should have done more practice on a bit of scrap. I did undercoat it you can just make out the white paint (the Acetone is old used stuff from decorating the house the other week). And the air pressure is tricky to get right, I've not airbrushed for a while. And it was a tad cold.

So! Plan B is try again with enamel, I do get better results with that stuff. And I'll give the airbrush another go before I get the paint brush out.

I'm undecided if it's really worth undercoating or priming aluminium before painting with enamel. I have painted bare metal without primer and it is still there after many years, so stand by for disaster number two!

Ian

mechman4809/11/2019 11:16:20
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2518 forum posts
377 photos

'I'm undecided if it's really worth undercoating or priming aluminium before painting with enamel'

That's a question I've asked myself; I have used gray etch primer followed by rattle can enamel on my other models but that's on cast iron, & all have been successful. I do have a mini spray gun that I bought off eBay but have not used that yet, but that still leaves the question 'best way to spray aluminium' I understand that cleanliness is a must plus a slightly abraded surface helps, so am keeping an eye on responses to this post.

George.

JasonB09/11/2019 13:04:23
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Particularly when using light colours the primer helps a lot to give the correct colour without excessive coats and you also get an uniform colour when spraying light coloured metal such as aluminium and darker iron where if you don't prime the CI darkens the look particularly on external edges where the film thickness is always at its lowest.

Must admit that unless I want a particular colour or finish the airbrush won't get used as rattle cans are easier and often more compatible with the clear fuel proofer I use on the IC engines as well as VHT for hot bits

Ron Laden09/11/2019 14:34:40
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1451 forum posts
256 photos

I use acrylics in cans and regardless of the material I always prime first, then a number of thin coats until I am happy with the finish and coverage. I never paint anything at less than room temperature and even increase it a bit if I can especially larger lumps or assy,s in metal.

Jim Nic09/11/2019 15:45:03
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213 forum posts
111 photos

I always use etch primer on aluminium and standard grey primer on other metals.

This is a picture of an engine (Jason's Jowitt design) with aluminium, steel and cast iron components treated as above which although my camera and the light may not show it well, are all exactly the same colour.

finished jowitt 7.jpg

Jim

Ian Johnson 109/11/2019 16:13:46
174 forum posts
50 photos

Mick B1 yes the colour was a bit bright! and in my defence I am colour blind! That's why I am not an electrician! So I'll tone it down a tad.

I do like the finish on Jim Nic's engine, so I'll be aiming for something like that, but a darker green, and satin / matt. And a thin undercoat is a good idea, but I am wary of building up paint thickness on a fiddly engine like my Stothert & Pitt, everything is a close fit.

We'll see what happens when I start mixing paint colours.

Ian

Hollowpoint09/11/2019 19:15:47
240 forum posts
28 photos

There is an excellent video on YouTube about finishing aluminium. IIRC it was one of Dan Gilbert's videos.

The best finish Ive ever managed on aluminium was by shot blasting and then using acid etch primer afterwards. One of the things I learned from the video was that you must paint aluminium very soon after preparing the surface as it starts to form an oxide layer within hours.

Jim Nic09/11/2019 21:58:58
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213 forum posts
111 photos

Ian the colour above is a Halford's rattle can called Ford Highland Green.

This engine is in Halford's Ford Meadow Green:

Hasbrouck rocking valve finished 2.jpg

If you are carefuland and apply thin coats then they don't come out too shiny.

If you want they can always be oversprayed with a thin coat of satin laquer to reduce the shine.

Jim

JC5409/11/2019 22:33:52
98 forum posts
1 photos

Just adding to a previous comment, when I worked for a vehicle maker several panels were made of aluminium we had quite a few complaints of paint coming off. I did a test of sanding panel and then etch priming after different lapses of time. We found that panels had best adhesion if etch primed within 30 mins of sanding. It is surprising how quickly ally will start to create an oxide coat after sanding!!!!!!

John

Mark Rand10/11/2019 00:51:54
798 forum posts

When painting flat surfaces it's fairly easy to splatter on a very light coat of black rattle can paint (the splatter is important) as a witness layer, then sand it down with the appropriate wet/dry paper until the splatter is mostly gone. After that, more top coat can be sprayed on and another trial of splatter and sanding. Eventually, you end up with a mirror finish (once you've worked down to 2000 grit paper, then buffing compound).

The downsides of the above approach are that is doesn't work very well with concave surfaces and it works even less well with mat or satin paints. crying

 

PS:- I do colours, but SWMBO and my lad don't. None of us have any great complaints about my Hardinge lathe. It was supposed stand out. RAL 6018 Apple Green laugh

 

Edited By Mark Rand on 10/11/2019 01:01:01

XD 35110/11/2019 02:50:19
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1362 forum posts
118 photos

I like deep brunswick green on my engines with red on the flywheels or machine grey with red in the flywheels , both are epoxy enamel paints like killrust or metalgaurd etc .

Ian Johnson 110/11/2019 16:38:33
174 forum posts
50 photos
Posted by Mark Rand on 10/11/2019 00:51:54:

PS:- I do colours, but SWMBO and my lad don't. None of us have any great complaints about my Hardinge lathe. It was supposed stand out. RAL 6018 Apple Green laugh

Edited By Mark Rand on 10/11/2019 01:01:01

'It was supposed stand out'! Mission accomplished! and wow does it stand out! Trouble now is, it's like a brand new car just waiting for the first ding! Nice job by the way.

I'm heading for something in-between Jim Nic's Meadow Green and this Apple Green

Ian

Neil Wyatt10/11/2019 20:00:08
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16740 forum posts
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Edited By Neil Wyatt on 10/11/2019 20:00:37

Mark Rand10/11/2019 22:53:07
798 forum posts



I was originally going to paint my HLV boring grey, like the original colour, but Macona on the PM forum painted his Monarch 10EE a beautiful red colour and that made me think that grey wasn't the only option.

 

The LNER colours have a soothing look. But there are a number of variants of those over the years.

 

Edited By Mark Rand on 10/11/2019 22:55:09

Ron Colvin12/11/2019 13:52:49
54 forum posts
3 photos

When paint does not remain attached to an oxidised aluminium surface, is it the oxidised layer that lifts?, or is there a weak bond between the paint and the aluminium oxide?.

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