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Thread: Coating rods

  1. #1
    GLSmyth's Avatar
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    Coating rods

    I am collecting materials to give making AZO a try and one of the last things on my list of things to get is a coating rod. I found some at http://www.gardco.com/pages/applicat...wound_rods.cfm (most other places force one to request a quote, so I assume that they are looking to sell in bulk). The thing is that I am not sure which one would work best. Does anyone have a recommendation or a better source?

    Cheers -

    george

  2. #2

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    George,
    If they are the same coating rod as for pt/pd check with Bostick and Sullivan in Santa Fe, NM. I have gotten glass rods from them and they come in different sizes.

    http://www.jeffreyglasser.com/

  3. #3
    dwross's Avatar
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    May I suggest this?
    http://thelightfarm.com/cgi-bin/html...tent=22Jan2013 (and there's a lot more info previous to and after this page.)

    Good luck and fun, whatever your technique!
    d
    www.thelightfarm.com
    Dedicated to Handmade Silver Gelatin Paper, Film, and Dry Plates.

  4. #4
    GLSmyth's Avatar
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    I initially posted that a puddle pusher would not work but have edited this post because it may. 35mm film is about 5mil in thickness and that is the clearance I need, so I may be able to place a strip on either side and place the puddle pusher over it, giving a 5mil clearance over the paper. A coating rod would be much easier (I have used one and it makes coating a cinch), but if I cannot figure out which size to get then I will be spinning my wheels.

    Watching at the video it looks like the poster has something on either end of the puddle pusher - attaching 35mm film should allow for the required clearance.

    Cheers -

    george
    Last edited by GLSmyth; 04-07-2014 at 12:54 PM. Click to view previous post history.

  5. #5

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    George,

    Didn't Ron (PE) have a recommendation?

    Fred

  6. #6
    dwross's Avatar
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    I think I'll amend "suggest" to "beg". Please take a look here:

    http://www.thelightfarm.com/Map/Pape...atingPart3.htm

    You are correct, of course. An unaltered puddle pusher only pushes the emulsion around. You need a gap between the paper and the coater. Wrapping tape around a glass rod creates a coating gap.

    There are a number of reasons this works better than a wire-wrapped metal bar. Silver emulsion will eventually corrode even stainless steel. Glass is corrosion-proof. It's dimensionally stable. Puddle pushers are cheaper. They are far more adaptable to experimentation and different emulsions because you easily set a custom gap height with tape.

    I don't even know how many acres of paper and film I have successfully coated, but it's a lot. I'm into my third pound of silver nitrate. I'm giving you good advice.
    www.thelightfarm.com
    Dedicated to Handmade Silver Gelatin Paper, Film, and Dry Plates.

  7. #7

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    George,

    Nick informed me that the wirewound coating rod we used in the AZO workshop last month is the RDS #130 'gapped' rod. Theoretical coating thickness is 11.7mils, well outside of the 5 to 7mil range that was recommended by Ron. I asked Ron about this and he guessed that the #130 rod was chosen mostly because it was available and for no other particular reason. RDS has many other rods available. Their #56 rod is listed at 5.04 mil coating thickness and the #80 rod at 7.20 mil.

    Here's a link to the RDS download page for specifications: http://www.rdspecialties.com/techinfo.html

    Of course, a glass rod wrapped in tape might work just as well and cost a lot less.

    Regards,

    Lee Rust

  8. #8
    dwross's Avatar
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    Is it possible there was a glitch in the communication? Coating thickness is considerably greater than final, dried-down thickness. 11-12 mil will dry down to 5 to 7 (generally, a good final thickness). I aim for a 10-12 mil gap. My guess is that's the reason the class went with the #130.
    www.thelightfarm.com
    Dedicated to Handmade Silver Gelatin Paper, Film, and Dry Plates.

  9. #9

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    Denise, the #130 wire wound rod with 11 mil gap worked fine and Ron's custom built edge coater with 5 mil gap also worked very well. Prints made from the thicker emulsion made with the rod did seem to have more contrast.

  10. #10
    dwross's Avatar
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    Hi Lee,
    That's the lovely thing about handcrafted. Each hand crafts as each heart desires. I favor the appearance that comes from a thicker coating of emulsion, but you make a really excellent point. There's a lot of wiggle room for technique and a lot of ways to get from Here to There.

    I hope you and George and the others in the class post here soon and often. You could revitalize the joint!
    d
    Last edited by dwross; 04-07-2014 at 07:08 PM. Click to view previous post history. Reason: striving to learn to spell
    www.thelightfarm.com
    Dedicated to Handmade Silver Gelatin Paper, Film, and Dry Plates.

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