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DIY Mayer Rod for Coating Carbon Tissues, Emulsions - Meyer, Metering, Wire-Wound Bar

So I take it the idea is to have a bar with a winding that is a bit wider than the width of what you're coating, plus handles on both ends? So, for say 8x10, you'd want it 9 (or 11) inches plus say 2 x 5 inches for 19 to 21 inches, total length?
 
holmburgers said:
Greg, are you measuring with a pair of calipers? I don't know if my pair are accurate to thous (I like that word...)
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Yeah...the face of my dial calipers are marked in 0.001", and it was about half way between 0.008" and 0.009".

I don't think a coating rod is appropriate for wet thicknesses like that. I don't think the RD rods go much above about a 20 mil wet thickness, which is a good thickness for more heavily-pigmented carbon tissue, or color tissues (perhaps even too thick for color...).

For reference the B&S gelatin + substrate thickness is only about 0.009-0.010.

holmburgers said:
So, for 8.0 mil dry thickness, based off of PE's formula, you would need a rod with 0000 gauge wire, 11.7mm diameter.
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That's not so much wire as rod stock. Good luck winding that around anything...

--Greg
 

Yes, that's true for large diameter threaded rods. Not so for thinner rods (say, <5mm). By the way, they're also available in various plastic materials - see http://www.fastenercomponents.com/threaded-rod.php
 
holmburgers said:
The problem however, is that these threaded rods are very coarse and have many imperfections which would likely lead to scratches.
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Use a precision Acme threaded rod. The thread form is better suited to this application since it does not have a sharp peak, and the rods are very finely polished. They're available in stainless steel, and don't cost much more than regular all-thread.

Check availability at McMaster-Carr www.mcmaster.com for folks in the US.

- Leigh
 
Vaughn said:
mdm -- there is nothing reasonable about the relief I get...

Vaughn
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I have spent the morning coating with a RD 200. It is very quick and easy to clean up, you just pop it back into its water filled gutter pipe and its ready to go next time. The tissue sets very quickly and can be moved very soon after pouring. It dries super fast, mine is already leathery after an hour in the cupboard with a dehumidifier. A normal threaded rod should work fine, at first I thought that is what I should have done, but the profile is different to a threaded rod, something that is much more noticeable on a RD95, and I am glad to have them. A threaded rod will be much harder to keep clean,if that deep valley fills with pigment or glop and once it dries you have a problem.

A rod is nice for sizing paper, even if you dont use it for tissue. Of course if you only use photopaper then you have no reason to size paper.

Thick tissue works fine but its more work at every stage, often a bitch to seperate. Also aparrently many high relief prints at George Eastman House are in bad shape, even in the Tod Gangler videos he mentions how they can crack where there is a change of relief. I decided that when I make a nice print one day it will last, but I do miss the relief sometimes, its the thing people notice about prints.
 
The cracking might be due to insufficient clearing of the dichomates. 1) they are usually (if not always) single transfer prints, so the dirchromate gets trapped between the gelatin and the final support and 2) the thicker print makes it more difficult to get the dichromate out.

It appears (but as far as I know not proven) that any dichromate left in the image will slowly cause the gelatin to harden further over time making the gelatin more brittle. Might not be an issue if the print is kept flat...if bent, the gelatin might crack.

But even thinner prints w/o relief might have these same problems if not cleared sufficiently. But double transfer prints generally need little or no clearing (other than a good wash) as the dichromate is easily removed by the double transfer itself.

Please note that I do not write this as an absolute authority on the subject -- but offer this as the consensus of opinion of some carbon printers on the carbon forum, based on research, etc.

Vaughn
 
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Seems to make sense. Perhaps it is another creative variable that can be used, high relief, low relief, tint, support paper, etc.
 
The difference between a coating rod and a coating blade is waste. If you are coating carbon, this is not an issue, but when coating silver, Pt or Pd, it can become an issue. There is generally more waste with a rod.

PE
 
gmikol said:
That's not so much wire as rod stock. Good luck winding that around anything...
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Yes; that was more a demonstration of the formula than anything.

The plastic or stainless steel threaded rods sound good. And not that it would be too hard to figure it out empirically, but I wonder what the relationship is between thread size and coating thickness?

Shoot... you could probably even use expansion springs. http://www.mcmaster.com/#extension-springs/=dbx0gj
 

Ballpark: coating = 1/10 wire diameter (round wire, packed). There are variants on the basic meyer rod: gaps between windings, double wound, machined (instead of actual wire). In the case of threaded rod, not just the depth of thread, but the shape of the 'valleys' need to be taken into consideration.

I actually tried using a expansion spring (the kind used for a garden gate) - it worked surprisingly well. Am I still using it? No
 
Oct workshop

Photo Engineer said:
That company is about 5 - 10 miles NE of George Eastman House. Mark has a few of them here IIRC, so those coming to the workshop in Oct. can try one out I guess.

PE
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Yes, I'd like to try that on a 12x15 inch glass plate. I suppose the plate would need to be surrounded by glass edge pieces of the same thickness and all pre heated.

Michael
 
Michael:

My method does not require dams in the sense that some other methods do. I can use one large blade and shim it down to any width. A blade can coat any length provided you have arms long enough! Due to the huge heat capacity of the steel blades, a heated plate is not necessary. It can be at room temperature, but heating can help a bit. I usually blow on the plate before coating. Mark Osterman does the same.

PE
 
Dust has been found in my emulsions, I have a bulb to use that will be put into play next time. Thanks for the heads up.
Pouring over the edges helps to prevent frilling or edge separation. It also reduces the size of a "picture frame" effect. That is a thinner border that forms when drying. A coating blade would need a pretty large well to coat a large piece of glass, but then, it does put emulsion on thinly.
 
I use a gold mesh coffee filter to remove most dust and dirt. It works very well.

As for frilling, I file a slight bevel on the edges of my plates to remove sharp edges and to give the edge a "tooth". Mark Osterman's influence again! The blade method gives an even coat except at the edges. The start and finish of a pass can introduce defects and that is where a "dam" is useful. You coat longer than you want and the dam is the part with start and stop defects. I use 12 ml of emulsion to coat 1 foot square at 5 mil undercut. I use about 15 ml at 7 mil. I usually coat plates at 7 mil.

An afterthought:

You can use a full width rod with cardboard or metal (SS) edge guides to act as dams. This will prevent the spread of the emulsion common to the use of these rods. If you use glass edge pieces, then they should be thicker than the plate you are coating, and of course the rod should be full width for the plate. I think that using the edge as a dam with most methods is as good or better than using shims, but they both work.

PE
 
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Just a quick update to this thread...

I started thinking again about Meyer rods and went back and looked at RD Specialties.

They have a section for Dead Link Removed and I emailed them for a price quote.

These rods will coat up to 12" wide and not one of their options (including formed rods) costs much more than.... drumroll please ... $30! Depending on your specifications, you're looking at probably $25, plus shipping.

For thicker carbon tissues you might have to get a "gapped" wound rod, but I can't say for sure.

Worth looking into if you're interested.
 
..or you can just get a threaded rod at Home Depot and adjust the % solids to get the desired thickness.
 
The advantages of threaded rods increases as the size of the tissue poured increases. A 20 inch rod is convenient for A3 or slightly larger pours. A 40 inch is a little harder to use uniformly but still makes large tissue pours really easy. A 12 inch rod may not be all that useful next to any other method of pouring, such as spreading with a comb or with hands, except they help to disperse bubbles quite well. Wasting a little glop is really no problem, you can just scrape it up and reuse it anyway. I use a 20 inch and a 40 inch RD200 with 12.5% gel for tissue and a 20 inch RD95 with 10% gel for sizing paper, only because those were the sizes in the group order that happened last year. The 40 inch allows me to effectivly pour 4 A3 sheets in 1 pour, a great time saver, and the smaller rod makes it easy to pour smaller sheets each with different tones or colours. A fairly coarse threaded rod should work fine as CMB suggests. Some people seem to prefer a hollow hot water filled pipe with magnetic strips to hold it up, that works ok too. Overall though, a threaded rod seems to be best at ferreting out the air bubbles and the simplest clean up.
 
The threaded rod scares me because they're all very rough looking (gnarly). Specifically I'm wanting a rod more like your RD95 for getting a thin coating, for sizing and carbon-matrix pouring. Comb is working great, but this option is just so appealing.

Shipping is less than $10, most LAB rods (12") are under $25, and there's no minimum or set-up fee and most are in stock ready to ship. That's $35 for a precision & purpose-built instrument of the highest quality. I'm happy to give them my money for this.
 
Home Depot has threaded rods here. They can be sanded down a bit and the oil can be washed off. Might be useful, IDK. At least you can see them!

PE
 
I agree it'd be worth exploring, but if time is money, buying one of these calibrated meyer rods might actually be cheaper.

Plus you'd have to experiment to find the right coating thickness with a threaded rod. But I have to say, if I were to ever need big sizes I'd be headin' straight for Home Depot!
 
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