Printing on black stompboxes

[ricbox]

So, I wanted to do a Marshall Bluesbreaker replica, like this


I've painted the box with a black spray paint and sprayed the clear coat to fix it.
The problem is that if I put a blue sticker on it, it basically just disappear with the background. How can I "fix" the blue correctly so that it doesn't get darker and unreadable? I've tried clear coating the adhesive before putting it on the box but it doesn't work.

Any help is appreciated.

[FiveseveN]

Paint the back of the stcker with (more or less opaque) white. Pigments are subtractive: blue paint is not blue in the same sense that a blue LED is, it's actually "minus everything else but blue". Black is "minus everything" or -∞, white is "minus nothing" or 0.
The light that isn't absorbed by the translucid blue gets absorbed by the black behind it. If that black were white, the light would be reflected instead so it would turn out blue.

[Paul Marossy]

The light that isn't absorbed by the translucid blue gets absorbed by the black behind it. If that black were white, the light would be reflected instead so it would turn out blue.

So then on the original it would be like a two step process with white background first and then blue on top?

[ricbox]

Paint the back of the stcker with (more or less opaque) white. Pigments are subtractive: blue paint is not blue in the same sense that a blue LED is, it's actually "minus everything else but blue". Black is "minus everything" or -∞, white is "minus nothing" or 0.
The light that isn't absorbed by the translucid blue gets absorbed by the black behind it. If that black were white, the light would be reflected instead so it would turn out blue.

what do you mean by "painting the back of the sticker"? If I put the white paint on the adhesive part of the sticker, shouldn't it not stick anymore?
Or maybe I have to paint white the part where the sticker goes...?

Thanks for the gradients explanation.

[FiveseveN]

The paint on the original is probably thick enough not to need any "backing".
ricbox, what kind of sticker are you using? Are you printing on a self-adhesive transparent medium? Try adding more toner/ink (using a high-quality/photo setting) or just switch to paper.

[cloudscapes]

You need to print on opaque stickers, not translucent.

[ricbox]

The paint on the original is probably thick enough not to need any "backing".
ricbox, what kind of sticker are you using? Are you printing on a self-adhesive transparent medium? Try adding more toner/ink (using a high-quality/photo setting) or just switch to paper.

Every sheet is 50 my (micron) thick, and it's adhesive transparent paper.

You need to print on opaque stickers, not translucent.

Maybe that's the thing. Here in Italy, this kind of paper isn't cheap and popular.

[davent]

The area on the enclosure where the sticker is to be mounted needs to be painted white. Print your sticker/label so you have a sticker with the blue lettering within a black rectangle that is a bit larger then the white painted area, as opposed to blue lettering on a clear background.  The sticker will hide the white paint and the blue lettering will show up the way you envisioned.

Other option, cut a stencil for the lettering, stick that to your enclosure, apply clearcoat (or the black paint) to the stencil, (seals the edges of stencil), apply white paint to stencil and finally the blue paint. Peel away stencil, touch-up and clearcoat.

dave