Thanks for the sketch. Could you email me the .skp file to email@example.com? Actually, I bet if you email it to Denise as well she'd be happy to put it on the Light Farm website.
My local plastics house has 1" thick acrylic (as well as the 1/2" like you used here). For your Rev. 2 coating blade, are you planning on simply extending the dimensions upward 1/2"?
You said "plexi" - is that the acrylic version of "plexi" or the polycarbonate (actually real) "plexi"? I can easily get acrylic at 1" but polycarbonate only up to 1/2".
Did you think of HDPE? Or VHMW or even UHMW Polyethylene - it's supposed to be similar in many properties to Teflon - low coefficient of friction, chemically resisitant, resisitant to abrasion. And can get them all cheaper locally than the acrylic stock.
There's a lot more hazardous things to worry about than the type of glycol used in a product... They are all so low in toxicity that it's a non-issue - for me. It's like worring about the differences in toxicity between KCl vs. NaCl.
I'm not real sure, but I think I used Lucite acrylic. There is no printing on the protective paper cover on the left over piece I have, though there was on the part I used. In its current form, this blade can only coat a 5 1/2" x 15" area. Not very economical if I cut a 6" strip off a standard 22x30 sheet of watercolor paper where I would like to get 3 5x7's.
I have some UHMW plastic in 3/8", it's not very rigid, it is very slippery. If I go the plastic route I need something that can be worked with woodworking tools and not need a special grind on saw blades and drills.
Originally Posted by Kirk Keyes
Yes, I can agree to an extent.
I try to keep the entire facts before the audience though because not all of them are chemists as we are.
The issues of the type of glycol and the concentrations which cover a range of 6x from Photo Flo 200 - 1200 makes a big difference in work flow due to the need to make up stock solutions and juggle amounts used. The different glycols take different concentrations in their own right.
So, it is not straightforward.
A comparison test
I tried adjusting the bromide & carbonate level of Ansco 130 to get a little more contrast out of this emulsion. Need to experiment some more, but I did get a little more contrast.
Here is an image of two prints made with the same negative. On the left a Kallitype toned in gold, printed about 6 mo. ago, and on the right the emulsion I am working with, mentioned in this post.
The prints where scanned at the same time.
Great results Tim, very impressive.
Originally Posted by Kirk Keyes
Not to cause you guys extra work ;)
but some people might not see how your (Kirk & PE's) two most recent comments on this meshes with PE's earlier comment:
Propylene derivatives are safe even as food additives but the Ethylene derivatives are deadly poisons and cause kidney failure.
Perhaps you could put this into perspective?
Simply put for me.... I always try to use the less toxic of two ingredients if there is a choice. I always try to use the most manageable product if there is a choice. And so, Photo Flo 200 is least toxic and most dilute. I can use 1 drop as an example (1/25th ml with my calibrated dropper). With Photo Flo 600, which is toxic, I would have to use 1/3 of 1 drop. That would be impossible requiring lab dilution of a toxic substance.
There is less handling of a virtually non-toxic substance as opposed to handling of a toxic substance in concentrated form.
I hope this puts it into perspective.
Originally Posted by Photo Engineer
I just deep fried my finger while making Calzone for dinner so that is enough perspective for me! Deep fried might taste better, but baking is safer!
If Kirk wants to expand on the how narrow the difference in their safety factors really is, thats fine too, but it looks like I'll be baking for the next few days!