Photoetch question

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Chumley
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Photoetch question

Post by Chumley »

All

I am not used to using photo etch so was hoping someone can help direct me

I have some p/e wing end plates and am thinking of using them on the next build.

However, is there a difference between the preparation for different types of p/e? I have brass, some silvery stuff (flat) and some highly shiny parts (s27’s BT52/MP4 wings)

Usually I would metal primer and then treat as usual. However of late, it seems that the paint chips very easily even after metal primer.

Do I need to sand them first?? I was under the impression that the whole point of metal primer was that it actually ‘etched’ the surface

TIA
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Re: Photoetch question

Post by PeteJ »

As you have learned, all photo etched is not made from the same metal and "color" is no indication of what the metal actually is. There are a lot of different alloys that PE makers use and they all react differently to paints and primers. Most are some alloy of stainless, but german silver(a copper and nickel alloy) is also common. You may also have plated copper though that is rare. Brass is a favorite because it works well with most paint. You really need to experiment with a piece of the sprue first before you finish the part.
One tip that I use with all PE is to soak it overnight in acetone. Many forms of PE have an oxidation inhibitor coating which can make a mess of paint. An acetone soak will get rid of most forms of coatings.
Next I always run a medium sanding stick over the whole sheet front and back. It may not be necessary but it will provide "key" for any paint to stick to, and also makes the glue work better on the backside. Worst case it isn't necessary but it does no harm.
Oh, and all primers are not self etching. Tamiya primer does work on metal but is not as aggressive at etching the surface as the stuff you get at the auto paint store, but the auto stuff is also generally thicker and more likely to obscure surface details like rivets.
Good luck and happy painting!
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Re: Photoetch question

Post by Chumley »

One tip that I use with all PE is to soak it overnight in acetone
Thanks, I had not heard of that before. I had lightly sanded the etched pieces on both sides though
Tamiya primer does work on metal
We’re you referring to the standard primer here? As I know they make a metal one (which I haven’t tried)

My efforts so far have been with Mr Hobby’s metal primer and I’m not that impressed, although that may well be because of my own lack of prep
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Re: Photoetch question

Post by PeteJ »

Chumley wrote: Sun Feb 21, 2021 1:27 am
Tamiya primer does work on metal
We’re you referring to the standard primer here? As I know they make a metal one (which I haven’t tried)

My efforts so far have been with Mr Hobby’s metal primer and I’m not that impressed, although that may well be because of my own lack of prep
All the primers that I know of that Tamiya sells are the same basic plastic/metal primer. Because they are lacquer based they will "self etch" plastic and metal to some degree. It is the strength of the solvent that makes them etch more or less. Automotive grade lacquer or catalyzed primers have a much "hotter" solvent and will etch the substrate more.

For most model builders, the Tamiya primer is quite adequate especially for plastic, but when dealing with PE of unknown alloy, you may need a stronger primer such at Plasicoat or Krylon. Just be aware that those paints do have a higher level of buildup so you may need to be careful you don't bury detail.
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Re: Photoetch question

Post by Terry »

I soak my photoetch in vinegar (usually for about 15 minutes) prior to using a metal primer. Trial a soak with a spare piece of etch fret to monitor how quickly it eats into the metal. It will vary depending on metal and thickness. The keyed surface will be smoother than sanding and gets around issues of having to prime over sanding scratches. I picked this tip up from a ship modeller who vinegar etched his railings so they become even finer and they also hold the paint better so enabling pre-painting prior to installing them. Don't forget to rinse the vinegar off the etch with water when done.

If you're looking for a primer only solution Gaia Multi Primer is very good but hard to come by especially in Covid times. Just be sure to clean your airbrush well straight after using it!
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Re: Photoetch question

Post by Chumley »

Ok so just thought i’d report back.

I decided to jump the gun on this and start on the p/e even though I am in the middle of another wip.

The p/e (MP4/5B wing end plates) looked like they may have been brass and was from an old f1 specialties set. I went about cleaning them with acetone; didn’t really notice any difference afterwards but there must have been some reaction as the acetone was green tinted afterwards.

They still looked dull (oxidation?) so i used some 1500 just to get them back to bare metal again. The 1500 was good enough to get the oxidation off but not leave scratches.

Soaked in vinegar (white, 5%) for 15 mins as suggested and then sprayed with (non metal) primer. 2 light coats followed by a few more of the base colour

Left overnight and then sprayed the other side.... held my breath to see if the other side was going to chip or peel..

Perfect!

Thanks for the tips all, very much appreciated thanks 🙏🏼
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