Positive etch resist
Posted 22 October 2012 - 02:55 PM
I thought it would be fun to do some freehand drawing on metal. That's when I came unstuck.
I found that there are surprisingly few pens/markers/paints that will go well on metal (brass in my case). I tried a few and this is what I found:
1) Pebeo pen - great resist when it sticks, but it beads up and is virtually useless for drawing. Ditto the Pebeo paint in pots
2) Sharpie - useless, washes off quickly. The industrial version of Sharpie is much better, but also has a tendency to bead up and one ends up with pinholes in the pattern.
3) Testor enamel paint (hobby paint) - see Pebeo.
4) Sakura Pen-touch - this is far and away the best paint for metal. Drawing was really easy with it, no beading at all. However, this marker only comes in white, silver and gold, none of these ideal to judge how good the coverage is. Having said that, as a resist it did really well except for the areas which, in retrospect, were covered rather thinly.
The Sakura people offered to send me a sample of another of their product which they thought might be suitable.
Meanwhile, given my inability to draw properly with a mouse using Inscape, I am taking the long way round, drawing the design on paper, scanning it and transferring on Press-n-Peel.
Posted 22 October 2012 - 10:04 PM
Would the Pebeo Pen and industrial sharpie bead up if the piece being etched were kept warm during application. Perhaps by working on one of those drug store heating pads "
To cure the pen hole-ing does layering of mask help? Could you layer with one product and touchup with another of a different color. ? Which of these products are compatible ?
Posted 22 October 2012 - 10:16 PM
"He who works with his hands - is a laborer,
He who works with his hands and his head - is a craftsman.
He who works with his hands, his head and his heart - is an artist."
St. Francis of Assisi
Posted 23 October 2012 - 01:09 PM
I tried to make my own asphalt resist in the past - twice. I did not like the process and did not like the product. IMHO there are better resists for negative etching. Using it in a makeshift pen is certainly a thought, though.
As to compatibility I have used the Pebeo pen routinely for re-touching holes in either Press-n-Peel or my usual primary resist for negative etching. In that application it works just fine.
One of the big differences between the negative and posistive etching is the surface prep: For negative etching I like to leave the surface with a little bit of "tooth". It allows the resist to adhere better. The etched areas usually get painted in some way and the non-etched areas, after resist removal, can be treated further to make them smoother. With the positive etching I like to make the whole plate really smooth and polished which then shows as a bright reflective pattern. This, however, makes adhesion of resist more problematic.
Posted 23 October 2012 - 01:20 PM
Posted 24 October 2012 - 10:45 AM
He suggested mixing it up (add ink until you get a pretty black mix) and then letting it sit out in the air to evaporate and thicken. In a day or two (I suppose this might be dependent on the temp and humidity) you get a nice consistency that for me painted very well with a small artist brush. I didn't notice beading on mild steel that was shiny (but not mirror shiny) and cleaned with acetone. It was a very consistent cover.
I used the "battery charger/salt solution" process for the etching.
Posted 24 October 2012 - 03:19 PM
BTW it cleans even better with ammonia or commercial cleaners containing 2-butoxyethanol (Simple Green).
Posted 25 October 2012 - 02:59 PM
I do think the "thickening" process makes a difference. I found it thickens to "model paint' consistency pretty quickly which is easy to paint with and stay "inside the lines" which for me is critical. I can't freehand a simple circle without laying a quarter down on the table!
Posted 30 October 2012 - 10:18 AM
Posted 31 October 2012 - 03:02 AM
Bob, Do you know what acids the Johnson's pledge works with, besides the salt solution and battery? Pru
No, I'm sorry I don't. I don't like playing with anything stronger than salt water. And believe me, it was a real stretch for my feeling of well being that first time I plugged in electricity directly attached to metal going into a bucket of water!! I sort of expected a great flash of light and for the whole neighborhood to go dark!
Posted 02 November 2012 - 01:39 PM
Sakura people kindly sent me a marker they thought might do the job in question. It's called "Solid marker Slim". I got the black version and tried it yesterday.
It goes on metal easily, but because of the blunt point detail is difficult to achieve. It does not bead up, in fact it has a somewhat waxy nature. It dries quickly and is easily removed by isopropanol or acetone.
I did a trial using this marker together with the Industrial Sharpie (which I carefully retouched using a magnifying glass) and a Pebeo pen as a control. I drew three boats side by side on brass finished to grey Scotchbrite. The new marker picture looked horrible and I thought the brass showed through in places. I really did not expect much.
I etched the plate today using a warm FeCl3 bath for half an hour with almost constant agitation followed by water rinse and Sodium Bicarbonate.
I was surprised by the excellent resist properties of the Solid Marker! No foul-biting at all! The Pebeo pen was as usual: Thin lines are OK but any wider coverage has issues. The industrial Sharpie showed spotty foul-biting which in this context was not terrible but not desirable either.
In conclusion this new marker is a superb resist if only one can solve the detail drawing problem. Perhaps drawing a crude outline and finishing with scratching off the unwanted areas.
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