Newbie question about masking over metallic paints

[Marcello Rosa]

Dear all

 

This is probably already addressed somewhere in the forum, but I could not find a clear answer, so I hope you can help me with a surefire "recipe".

I am trying for the first time to do an all metallic finish, but having a terrible time because every time I try to mask, the previously painted metallic layer comes off. The paint job is not entirely ripped off, just part of the last layer. This has made this build not enjoyable at the moment, as I am stuck in this eternal cycle of re-doing what I thought was done.

A clear recipe to try next time would help, but at the moment I would be happy with direct answers to a few questions:

1. Do you think it is necessary to sand between layers, and if so what grit do you use?

2. Do you think it would help to insert a clear coat between layers? If so, would floor polish or a clear lacquer be better?

At the moment I have a base coat of Alclad black, and a first layer of Tamiya X-11 (chrome silver). These are staying fine. But whatever I try to paint on top is coming off (again, not entirely, but in isolated bits)

 

Thank you in advance

[Mark Harmsworth]

My best guess is that your problem is a result of the paint not adhering to the plastic properly and so lifts off with the masking tape.

 

This is what I do:

- clean the plastic with isopropanol alcohol applied with a cotton bud

- spray primer (for metallics I use a gloss black primer)

- wait overnight

- spray metallic

- wait overnight

- mask

- etc etc

 

So, from my perspective. I would say 'no' to both your questions.

 

I use acrylics and the paints I normally use are Ultimate primers and Vallejo Metal Color for the metallics. I have (almost) never had paint lifting after masking.

 

This example had a lot of masking after the metallic and is before applying decals:

 

Good luck

Mark

[Marcello Rosa]

38 minutes ago, Mark Harmsworth said:

My best guess is that your problem is a result of the paint not adhering to the plastic properly and so lifts off with the masking tape.

 

This is what I do:

- clean the plastic with isopropanol alcohol applied with a cotton bud

- spray primer (for metallics I use a gloss black primer)

- wait overnight

- spray metallic

- wait overnight

- mask

- etc etc

 

So, from my perspective. I would say 'no' to both your questions.

 

I use acrylics and the paints I normally use are Ultimate primers and Vallejo Metal Color for the metallics. I have (almost) never had paint lifting after masking.

 

This example had a lot of masking after the metallic and is before applying decals:

 

Good luck

Mark

Thank you for this. I have not tried the Vallejo acrylics, but may try it before I start a more ambitious project (a B-36).

I did use a gloss black primer (Alclad), and as I mentioned the chrome silver (Tamiya enamel) is staying put. My problem is coming from the next layers not staying adhered to the chrome silver (doing this to give some burned appearance around the engines).

[Alex Gordon]

I had something similar in my Percival Prentice build back in 2014.

 

 

I was using enamels and I sorted it by gently wiping it over with a bit if white spirit moistened bog roll.

[Marcello Rosa]

7 hours ago, Alex Gordon said:

I had something similar in my Percival Prentice build back in 2014.

 

 

I was using enamels and I sorted it by gently wiping it over with a bit if white spirit moistened bog roll.

At what step you did this? I guess, after the first metallic layer was dry but before applying the mask?

[dnl42]

@Mark Harmsworth presented a great recipe! My approach is quite similar. I'll use cotton pads from SWMBO's stock and cotton buds for cleaning with IPA. Make sure to always wash your hands before handling the model after this point.

 

You might also want to detack masking tape by applying it to your clean palm or a smooth clean surface before applying to the model. Tamiya Masking Tape is highly recommended!

 

The OD anti-glare panel, black stripes, blue stripe, and panel color variations were all masked atop the base coat. Some more photos are here.

 

[busnproplinerfan]

41 minutes ago, dnl42 said:

@Mark Harmsworth presented a great recipe! My approach is quite similar. I'll use cotton pads from SWMBO's stock and cotton buds for cleaning with IPA. Make sure to always wash your hands before handling the model after this point.

 

You might also want to detack masking tape by applying it to your clean palm or a smooth clean surface before applying to the model. Tamiya Masking Tape is highly recommended!

 

The OD anti-glare panel, black stripes, blue stripe, and panel color variations were all masked atop the base coat. Some more photos are here.

 

I've had tamiya tape take a bit of the metallic off, jut not as bad. This is a good topic. I wonder if a coat of some kind of clear on the silver first. I know it's a problem if your doing chrome or polished aluminum.

[dnl42]

49 minutes ago, busnproplinerfan said:

I know it's a problem if your doing chrome or polished aluminum.

Ya, assuming you're talking about Alclad, those two are very fragile. Last time I used Alclad Chrome, my finger was able to rub it off in casual handling. 

 

FWIW, I don't recall Molotov Chrome being as fragile, but I may be under-remembering.

[Alex Gordon]

3 hours ago, Marcello Rosa said:

At what step you did this? I guess, after the first metallic layer was dry but before applying the mask?

The matt black primer had around 6 hours drying time,the top coat had around 48 hours before the masking went on.

[busnproplinerfan]

7 hours ago, dnl42 said:

Ya, assuming you're talking about Alclad, those two are very fragile. Last time I used Alclad Chrome, my finger was able to rub it off in casual handling. 

 

FWIW, I don't recall Molotov Chrome being as fragile, but I may be under-remembering.

Ya, Alclad, it's nice but you have to be gentle. I used spaz stix chrome and it's quite good and durable, a bit more durable and you get more for the same price. Same method as alclad, but it only comes in chrome.

[malpaso]

I’ve masked over Vallejo Metal Color on Halfords primer without problems, but left the primer and then the metallic to cure for some days first.  When I was doing a lot of different metallics (on Razor Crest) I did spray a coat of Klear over the base aluminium layer, to be fair the multiple later layers of VMC weren’t affected by masking.

 

That said I’ve become wary of leaving Tamiya masking tape on any finishes for more than a few days.  I found it’s no good having time to do a massive masking session and then having to leave the masked up model for a couple of weeks for the painting opportunity!   This is on paint, varnish or metallic.  Just need to project manage effectively!

[Planebuilder62]

When using hi shine NMF like Alclad chome I paint the NMF backwards. This means mask different panels in the non- chrome shades avoiding putting the masking tape over these panels. I have found Alclad comes off quite easily when applied over a Tamiya gloss black base. If you do need to mask over these panels then damp 70 gr white printer paper works very well. You need to be quick with the masks because they fall off as they dry out.

 

When all thats done, mist over the chrome in thin layers. If it goes on too thick it will cause the underneath layers to crack. My NF-104 build in the WIP some time back has some pictures.

 

regards Toby