Brass preparation for painting

essdee
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Brass preparation for painting

Postby essdee » Mon Oct 11, 2010 9:30 am

Can someone remind me please, if the use of cream cleaners such as Jif, Cif etc to prepare etched brass for painting is a bad idea? I note Alan Goodwillie has used referred to the use of Vim on his Starting in P4 thread, and have a suspicion that additives in the other cleaners I mention above will hinder the adherence of paint.

Many thanks,
Steve

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Andy W
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Re: Brass preparation for painting

Postby Andy W » Mon Oct 11, 2010 11:21 am

I've just prepared 7-8 coaches for painting. I used Cillit Bang and Shiny Sinks to clean the brass, washed with lots of water, then applied an undercoat of car primer. So far the primer has stayed on!
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Julian Roberts
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Re: Brass preparation for painting

Postby Julian Roberts » Wed May 13, 2020 1:14 pm

Looking for advice on this subject (it's the aspect of modelling I get very little practice at, being so slow) it was a bit disappointing that this thread is so brief! The thread by Allan Goodwillie on making locomotives has a useful section on this page viewtopic.php?f=39&t=666&start=125, as do other topic headings in this Painting and Weathering section of the Forum. I have added a thought on Allan's second part to his loco building series which covers painting, on a possible alternative to Carr's Acidip (which is also referred to on this part of the Forum viewtopic.php?f=17&t=4938) at:

viewtopic.php?f=39&t=886&start=25

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Andy W
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Re: Brass preparation for painting

Postby Andy W » Wed May 13, 2020 2:03 pm

If your top coat is going to be enamel and grey, green, blue or black then the Tamiya grey surface primer is excellent stuff. It gives a lovely surface - but not suitable for cellulose finishes. Also for red and yellow it might be better to use a red oxide - Halfords?
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Re: Brass preparation for painting

Postby Julian Roberts » Wed May 13, 2020 3:33 pm

Andy that is useful to know, thanks. But it is the preparation (specifically, the cleaning) of the brass model, before the application of primer, that was my concern just at the moment. Is your recipe using Cillit Bang and Shiny Sinks still your preferred one? No one else has raised any further thoughts to it these last 10 years! I couldn't get any Shiny Sinks last weekend. Cillit Bang comes in several versions. The limescale remover one contains phosphoric acid as does (apparently) Carr's Acidip - though I wonder if phosphoric acid is critical or incidental.

Philip Hall
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Re: Brass preparation for painting

Postby Philip Hall » Wed May 13, 2020 3:55 pm

So far I’ve used Shiny Sinks (as suggested By Martyn Welch) and this has been fine. Followed by a rattle can of Halfords finest, grey or red.

Philip
Last edited by Philip Hall on Thu May 14, 2020 12:25 am, edited 1 time in total.

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David B
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Re: Brass preparation for painting

Postby David B » Wed May 13, 2020 5:06 pm

I have used at various times Shiny Sinks, Cillit Bang, Viakal and liquid soda (sodium hydroxide). Whatever you use, it needs rinsing thoroughly with water. I also give the items a session in an ultrasonic bath which, even after cleaning with any of the above products, still knocks off more crud. After that, I leave to dry under a cloche, the type used to cover a seed tray. This is to keep dust off before painting.

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John Bateson
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Re: Brass preparation for painting

Postby John Bateson » Wed May 13, 2020 5:23 pm

I find that the use of Cif (formerly Cilit Bang I think) always reacts with the solder on a model, leaving a dark surface layer that can be rubbed off with a finger. Once I have cleaned using this I always take a fibre glass brush over these surfaces to remove this residue.
I think the only solution (sorry) is to get everything as shiny as possible then a bath of the ultrasonic persuasion. Immediate use of hair dryer and then an etch primer.
John

PS - then put the hair drier back where it belongs!
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shipbadger
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Re: Brass preparation for painting

Postby shipbadger » Wed May 13, 2020 5:35 pm

Cif used to be called Jif. Name was changed so that it could be used across a number of countries. A bit like Marathon bars becoming Snickers.

allanferguson
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Re: Brass preparation for painting

Postby allanferguson » Wed May 13, 2020 6:54 pm

We used to leave pennies in a glass of Coca-Cola overnight and in the morning they were like new. I now know it was the phosphoric
acid which did the job, but would it still work?

Allan F

Julian Roberts
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Re: Brass preparation for painting

Postby Julian Roberts » Wed May 13, 2020 7:25 pm

Re Allan's post just above, what I don't get is this: we use phosphoric acid flux....which makes crud...we then use phosphoric acid.... to get rid of the crud!(?)

There seems to be more traffic on this thread than where I posted this idea, a citric acid "pickle" to, I assume, do the same thing. So I'm putting it here as no one has referred to it, though Will and Terry and Philip have replied on the other thread (thanks to all.)
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Andy W
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Re: Brass preparation for painting

Postby Andy W » Wed May 13, 2020 7:46 pm

The brass doesn’t have to be shiny - just clean. The primer will show any problems which can be addressed before your top coat is applied.
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Le Corbusier
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Re: Brass preparation for painting

Postby Le Corbusier » Thu May 14, 2020 6:43 am

f course there is always this approach ..... viewtopic.php?p=71271#p71271
Tim Lee

Daddyman
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Re: Brass preparation for painting

Postby Daddyman » Thu May 14, 2020 7:47 am

Julian Roberts wrote:Re Allan's post just above, what I don't get is this: we use phosphoric acid flux....which makes crud...we then use phosphoric acid.... to get rid of the crud!(?)

There seems to be more traffic on this thread than where I posted this idea, a citric acid "pickle" to, I assume, do the same thing. So I'm putting it here as no one has referred to it, though Will and Terry and Philip have replied on the other thread (thanks to all.)


The active ingredient in Shiny Sinks is Citric Acid Monochydrate, whatever that is - perhaps not very different from your "pickle". I've never seen it in supermarkets and have had to get it at proper shops, but it's available here, post-free, for £4.75:
https://www.ebay.co.uk/itm/Homecare-Shi ... SwhglTxzTs
I find it needs gentle scrubbing with a brush to really work (a soft paint brush). I used to leave models in it overnight, with no scrubbing, but that had very little effect on the model's cleanliness. Now I do a 5-10-minute soak and then use the brush.

To those using ultrasonic baths, what is your method? Mine has a maximum cycle of 8 minutes, and I tend to use it on that. I also use hot water (the hottest the tap will produce) and some squirts of Flash in there (this is after Shiny Sinks). This is fine in that it gets the models clean, but it also attacks superglue joints (for example where resin parts are stuck on), and also teases Milliput out of cracks. Does this just go with the territory, or should I abandon the Flash and/or hot water? Thanks.

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Andy W
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Re: Brass preparation for painting

Postby Andy W » Thu May 14, 2020 8:41 am

I use an ultrasonic bath when I think there may be some fibres or flux lurking around, but I only add tepid water. The machine should heat up itself.
Don’t get too scientific about this, take the simple route. Clean, protect from dust under a see through container then spray with a primer. Dust is the big enemy. I spray in the garden when the weather is fine and always warm both paint and model in the sun first.
I never got on with etching primers. I can only remember one problem I’ve had with Halford’s primer - an area of oxide fell off for no apparent reason. Perhaps the brass was too shiny? So I rubbed the area down with v fine wet and dry and resprayed the affected area. All was well.
I think the KISS theory works well in modelling.
Make Worcestershire great again.
Build a wall along the Herefordshire border and make them pay for it.

Julian Roberts
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Re: Brass preparation for painting

Postby Julian Roberts » Sat May 16, 2020 8:27 am

Absolutely Andy, re the KISS principle. I wonder if people find an ultrasonic bath like this is typical and adequate - I'm pleased to see it's not a very expensive bit of kit to possess:

https://www.wish.com/product/5c1720177f ... &share=web

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Flymo748
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Re: Brass preparation for painting

Postby Flymo748 » Sat May 16, 2020 9:50 am

Julian Roberts wrote:Absolutely Andy, re the KISS principle. I wonder if people find an ultrasonic bath like this is typical and adequate - I'm pleased to see it's not a very expensive bit of kit to possess:

https://www.wish.com/product/5c1720177f ... &share=web


Hi Julian,

That does look a pretty good price. I paid around £20-25 for mine in the now defunct Maplin. I didn't bother with any reviews, but it seems I chose a decent one by chance https://www.jewelry-secrets.com/Blog/cd-7800-ultrasonic-jewelry-cleaner-review/. The review may be a bit of a guide of what to look for.

The main thing is size. mine is large enough for tank engines, and smaller Victorian tender engines. If you're planning on building a Duchess, or Mark 1 coaches, then you may want something larger, and have to pay a bit more. But that would be better than having one that doesn't do what you need it to do.

Given you're buying online, and there are so many of these of variable quality coming out of China, I would do a little bit of research to find some reviews, even at that end of the price scale. The last thing you want is one with dodgy electronics.

I'd whole-heartedly recommend mine, but I don't think I can find it on sale online except at a greatly elevated price.

All the best,
Flymo
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Winander
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Re: Brass preparation for painting

Postby Winander » Sat May 16, 2020 11:41 am

Being interested in purchasing an ultrasonic cleaner, I found these sites explaining frequency useful https://www.upcorp.com/blog/how-frequency-relates-to-ultrasonic-cleaning/, https://www.omegasonics.com/ultrasonic-cleaning-2/how-do-i-know-what-frequency-i-need-for-my-ultrasonic-cleaner/.
I have seen comments that some of the cheaper end of the market use lower frequencies. Something north of 40 kHz appears to be suitable for our applications, based on the above links.
Richard Hodgson

davebradwell
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Re: Brass preparation for painting

Postby davebradwell » Sat May 16, 2020 8:15 pm

We used to have a "vapour blaster" in our amazing workshop at work which fired fine aluminium oxide particles and left a nice very clean satin finish. Some of the other modellers at work used to sneak along there and clean up their efforts as it would quickly remove any excess solder. I believe hobby versions are available - any experience out there?

Regarding primers, not so long ago I pulled a piece of n/s out of my drawer and sprayed the bare, uncleaned surface with gloss Humbrol black. It seems to have stuck far better than any of my more refined methods with Shiny Sinks, etched primer, etc. I just can't shift it and it's stuck right up to the edge. I haven't had a chance to follow up with more tests but I'll call for comments, please. Are we overcooking the problem? I remember a Railway Modeller years ago when someone used varnish as a primer as he said the pigment and possibly the matting agent affected adhesion - does he have a point? Our etching primers are meant to be used on steel car bodies - does the chemistry still work on brass and n/s?

DaveB

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MarkS
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Re: Brass preparation for painting

Postby MarkS » Sat May 16, 2020 8:26 pm

Cheers,

Mark.
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Julian Roberts
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Re: Brass preparation for painting

Postby Julian Roberts » Sat May 16, 2020 8:48 pm

davebradwell wrote: Are we overcooking the problem?
DaveB


Well, quite! - I really wonder the same. Because I only finish a model and actually get to do a paint job every 18 months or so, I get quite nervous with all the warnings "Don't skimp this stage" "A poor paint job can ruin the best model" and so on. So I go to huge lengths to get the model clean, yet find the paint goes on perfectly easily and it's a devil of a job getting it off where I don't want it! - slide bars on the Compound for example. Well maybe that's because of all the care I've taken.

But I've gone round in circles with the Compound. The last stage was to leave it to dry thoroughly as the boiler is full of lead shot and that had to dry out (I figured) after the model was immersed first in white spirit, then Flash, then having to get rid of the blue colour with fibre brush, then rinsed thoroughly with toothbrush, Vim and water. Yet after all that, having dried a few days there was a new layer of crud on some surfaces that ahem have a miscroscopic layer of solder. There was only one thing for it, out with the glass fibre brush again, and then give it a good blow (as in blowing a candle out), and get painting. - So much for the glass fibres being the worst enemy! And after all that, the Halfords primer seems touchwood to be fine, and I can't detect any glass fibres so far. (As for the chassis, that's been an even worse story)

An ultrasonic bath seems an attractive (and, using no chemicals, I would think kinder on the environment) way round all that, and thanks folks for your contributions. Looking just now online at a model that is around £50 (rapidly becoming a more expensive idea...!) I couldn't find a figure for the Khz at which it works...nor for the £17 model I mentioned earlier - but maybe that's my ineptitude with online research...

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Guy Rixon
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Re: Brass preparation for painting

Postby Guy Rixon » Sat May 16, 2020 8:52 pm

Julian Roberts wrote: I couldn't find a figure for the Khz at which it works...nor for the £17 model I mentioned earlier - but maybe that's my ineptitude with online research...


The £17 one says it runs at 40 kHz, which is encouraging.

Philip Hall
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Re: Brass preparation for painting

Postby Philip Hall » Sat May 16, 2020 10:06 pm

I remember in the early days of my modelling reading an article by ‘Robbo’ Ormiston-Chant (remember him, no prizes for old age!) and I’m sure a painting recommendation was a coat of ‘Valspar’ gloss paint on a whitemetal body. Apparently it soaked into the whitemetal a bit and formed a good base for subsequent paint. Of course this was before airbrushes and fancy paint became the norm, but it does seem to gel with Dave’s experience of gloss Humbrol.

I spray, or brush paint, a chassis, with black matt or satin car spray, and this seems to stick pretty well. Dave, was your Humbrol from a tin, through an airbrush, or from a spray can?

Philip

Stephan.wintner
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Re: Brass preparation for painting

Postby Stephan.wintner » Sun May 17, 2020 2:05 am

There's some discussion of using grit blasting to prep for paint in this other thread : viewtopic.php?f=39&t=3837&p=75447#p75447

Stephan

Daddyman
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Re: Brass preparation for painting

Postby Daddyman » Sun May 17, 2020 7:31 am

davebradwell wrote: Regarding primers, not so long ago I pulled a piece of n/s out of my drawer and sprayed the bare, uncleaned surface with gloss Humbrol black. It seems to have stuck far better than any of my more refined methods with Shiny Sinks, etched primer, etc. I just can't shift it and it's stuck right up to the edge. I haven't had a chance to follow up with more tests but I'll call for comments, please. Are we overcooking the problem? I remember a Railway Modeller years ago when someone used varnish as a primer as he said the pigment and possibly the matting agent affected adhesion - does he have a point? Our etching primers are meant to be used on steel car bodies - does the chemistry still work on brass and n/s?

DaveB


A few years ago I was with Ian Rathbone on a weekend course at Missenden Abbey and he told me that if parts have been half-etched (like the tender sides on your NER tenders, Dave, for example), or if they have been scrubbed with a fibre-glass brush, then there is no need for etching primer, as the microscopic roughness of the surface in both cases (after half-etching, after fibre-glass brushing) gives the paint something to stick to. And I've just opened A Modeller's Handbook of Painting and Lining at his chapter on priming, which begins, "If a model has been thoroughly cleaned, as outlined above, paint will stick to it without a primer. In fact the vast majority of models running today have not been primed and, apart from the exposed edges, the paint is still in place." I'm not quite sure how he gets to the calculation of "the vast majority", and as for exposed edges, well, there's the rub!

He goes on: "The principal use of a metal primer is the prevention of rust on steel. This is what your average car primer does, as it contains a rust inhibitor, which is usually zinc phosphate. The primer does NOT [his emphasis] have improved paint adhesion. It is designed for use on steel, to which paint adheres well anyway. When used on non-ferrous metals it is no more than an undercoat [my emphasis]." He then says the "real" primer is etching primer, "which has an important job to do on non-ferrous metals. After application, an acid in the mix, over a period of 12-24 hours, eats into the metal surface, creating the microscopic roughness that the paint requires to improve adhesion." (This acid, he says later, is our old friend phosphoric acid!) Two top tips for etching primer (as opposed to car primer) are (1) this thing about leaving it for 24 hours (for the Precision two-part primer) (don't touch it at all during this time - who knows what the blend of finger-print grease and, these days, alcohol-rich hand sanitiser, will do to mess up the process); and (2) it can (should?) be thin enough that it doesn't obscure the different colours (brass, whitemetal, resin, solder) beneath; you can then put a primer of your choice on over the etching primer - any Humbrol matt would do, or, if you insist, something from the dreaded aerosol.


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