Shotty Looking Finish?

[BobFrapples]

Hey guys, was trying a new finishing technique on some plates to see if I could get a "swiped" look.
Basically the overall was a gloss finish, then I used a Mr Clean Magic Scrub with acetone to take off the compound. Dipped in degrease, passed wb, dipped in deox, and went to ano.

36 sq in, placed in for 70mins, (0.8mm, 8CD, 2 A). Went to dying process.
Usually when I put objects in, they take dye right away, but this didnt, so I figured it was a thinner coat, maybe it took awhile. But I left it for 20mins, and it barely took any colour. Looks like a transparent purple, and the edges of the piece didn't take.

Any Idea on why it was so crappy? The tank was a little cold, low 60s. Whats the effect of a cold electrolyte?

[dmiom]

Originally Posted by BobFrapples

.....Usually when I put objects in, they take dye right away, but this didnt, so I figured it was a thinner coat, maybe it took awhile. But I left it for 20mins, and it barely took any colour. Looks like a transparent purple, and the edges of the piece didn't take.

Any Idea on why it was so crappy? The tank was a little cold, low 60s. Whats the effect of a cold electrolyte?

Bob - I think you've answered it already yourself!

Cold tanks build up a fine grained matrix. It is harder, and builds at a slower rate - so (a) using LCD type current densities it takes a lot longer (and can be more vulnerable to dissolution) and (b) the finer matrix is less able to accept the dye molecules. Taken to the extreme, cold tanks (37 - 40 F), high current densities and vigorous pumped agitation are used to make type III anodising - which is almost immune to dying.

Would suggest you re-run at nearer the LCD recommended 68-70F.

We had this when started - some of the first pieces we ever did were a great disappointment - black turned out just like it had been rinsed briefly in ink and left a blue-grey or blue-black sheen, not a proper coating. Then found we were only running at just about 60F.... Before getting a combined chiller/heater we used a handful of the cheap pyrex-clad 300w thermostatic aquarium heaters to get the tank up to operating temperature.

Dave

[BobFrapples]

Thanks Dave, I'll look around for a small heater today while I'm out.