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dannykalkhoven
10-21-2005, 05:16 AM
Greetings everyone

I work with modified 6X6 and 6X9 camera's, and very pleased with the results.
However, when there is sunlight shining on the fornt of the camera, a ugly yellow semicircle-strike pops up. The reason (i suppose) is that the edge of the thin copper foil i use for the pinhole is very shiny in bright light.
Does someone have suggestions to 'de-shine' the holes ?
Ink or paint is much to thick, it blocks the pinhole. I am considering aluminium instead of copper foil, but then the yellow strike is replaced by a silvery one...

earlj
10-21-2005, 08:26 AM
I use a black permanent marker (Sharpie brand) to blacken the inside of the hole and the back of the pinhole material. The ink from this pen is not thick, and the hole diameter does not seem to be affected much. I also sand down both sides of the pinhole material with emery cloth, both to remove any burrs and to make the area around the hole as thin as possible.

ImageMaker
10-21-2005, 11:23 AM
I'm with Earl on all counts -- though I did manage to completely block the hole in my recent 35 mm conversion after blackening both sides of the brass with the Sharpie, then coming back on the back side to fill in some areas that were thin. Fortunately, a very gentle poke with the needle opened it up, removing the ink (and/or whatever the ink was holding in place in the hole) without disturbing the metal edge of the hole.

murrayatuptowngallery
10-22-2005, 07:17 PM
Silver and copper will dull and darken in Kodak Selenium Toner. I can't speak for other types. Might work on brass too due to the copper content.

On copper, a dark dull grey results, but it seems delicate - comes off easily.

I don't know if it's toxic as selenium reportedly is.

M

dannykalkhoven
10-28-2005, 01:16 PM
Update on darkening shiny copper edges

Thanks for the advice. The permanent marker doesn't work with me, it keeps blocking up the pinhole, which is only 0.2 millimeters wide..
When looking (once again) around on the internet, a possible solution came up.
When making tiny scale models of trains etc, people want to make copper look old.
Their trick: take a cup , fill bottom with 'ammonia' (dutch word for a sort of cleansing fluid), put copper foil above it, cover the cup. The gasses that come up (ammoniakgas) stains the copper into a dark black-blue. Leaving it there for a day or two, i am now the proud owner of some very dark and non-shiny pinholes.
First roll has been exposed, in a few days i'll know more.
Look for the pictures in the color-pinhole section, when i've found out how to upload.
Danny Kalkhoven

ImageMaker
10-28-2005, 02:39 PM
Nice work -- most likely the cleaning fluid you're talking about is ammonium hydroxide, sold in the USA as "household clear ammonia" (Parson's brand is pretty common), and the gas is pure ammonia, which evaporates off the water solution when it stands.

That's one small hole -- got a very short projection distance?

taco
10-28-2005, 05:15 PM
Their trick: take a cup , fill bottom with 'ammonia' (dutch word for a sort of cleansing fluid), put copper foil above it, cover the cup. The gasses that come up (ammoniakgas) stains the copper into a dark black-blue. Leaving it there for a day or two,
If you do that, do it OUTSIDE. Ammonia stinks like hell

ImageMaker
10-28-2005, 05:47 PM
Well, the amount in a single cup wouldn't be all that big a deal if it's in a ventilated area. Still, better to put it on the range top with the exhaust fan running, or indeed outdoors, in the garage, or otherwise out of living areas; some folks can have serious reactions to breathing even low levels of ammonia.

murrayatuptowngallery
10-29-2005, 06:38 AM
It do stink, especially if you use the commercial stuff.

Hmm, I seem to recall that lye (sodium hydroxide) causes some drastic change in aluminum. I don't remember if it's black.

Ammonia solution or lye might do something for aluminum foil pinholes.

ImageMaker
10-29-2005, 01:45 PM
Hydroxide type alkali solutions such as ammonia and lye will simply dissolve aluminum. They react with the (usually protective) oxide layer and convert that, and the unprotected metal undeneath, to semi-soluble and very fluffy aluminum hydroxide. Lots of heat is evolved along with highly flammable hydrogen gas. And even if you could get it to stay in place, aluminum hydroxide is very white in color.

The only ways I know of to blacken aluminum are anodizing (hot sulfuric acid and electric current, then a dye to load up the thick and very porous oxide coating before sealing it in boiling water) and various kinds of paints. It might be possible to treat with a manganese or titanium bearing solution and make a very dark synthetic sapphire coating (similar to natural blue-black or green-black sapphires), but the problem with both anodizing with dye and an impurity colored anodize are that both typically involve adding .002" to .005" thickness of the anodize coating to the surface of the material -- which would completely close off a small pinhole, and significantly change the size of any hole we'd use in a reasonably portable camera.

murrayatuptowngallery
10-31-2005, 01:23 AM
OK, back two threads to copper.


Murray

dannykalkhoven
11-21-2005, 04:13 PM
Warnings:

Yes, it really is a very sharp and unpleasant smell, so don't use it in the living room!

Yes it works fine, but don't let the copper foil stay in the gasses for the whole night, see the result here http://f295.tompersinger.com/cgi-bin/Blah/Blah.pl?b=cm,m=1132600598

And finally: when you managed to make a good pinhole camera, don't spoil it! Just build a new one, so your first one stays OK! I found out the hard way...

Danny

ImageMaker
11-21-2005, 04:22 PM
Aaah, rediscovery of the ancient wisdom: "If it ain't broke, don't fix it!"

JoeVanCleave
11-21-2005, 08:01 PM
I've heard of this, and can't verify, but you can supposedly "smoke" a pinhole black using the soot from a smokey candle or other flame.

I usually attempt to shield the pinhole from direct sunlight whenever possible, although that's harder to do with ultra wide angles of view, without being part of the composition. Most of my cameras are moderate angles of view, so its easier to use a hat, or your hand, or just your shadow, to shield the camera.

I also try to arrange the composition so its side-lit, rather than pointing directly at the sun.

Of course, those artifacts from sun flare are part of the attraction that some have towards the pinhole medium, the unpredictable outcome can be serendipitous.