harbor freight micrometer

Dichromated Gelatin.
Joe Farina
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harbor freight micrometer

Post by Joe Farina »

I finally had a chance to test this (item# 98485, price $35) and it works well for measuring emulsion thickness (very easy to use). I did some coatings with a 10% gelatin concentration (Jeff's MBDCG with slight variations) and the results were as follows. (The Mayer bars were from RD Specialties.)

#24 bar.....14 microns
#36 bar.....17 microns
#48 bar.....19 microns
#60 bar.....25 microns
Tony

harbor freight micrometer

Post by Tony »

Nice Joe

Can you discribe your method?
Did it measure a single ply of film?
Or did you scrape film off and measure glass vs glass and film?
Was this pre exposure film or post exposure?

I found there are mic's that as you rotate the knob the piston part does not spin. these tend to be the best (IMO)

However it is hard to get a consistant reading and that it ends up being an average of several measurements. I hope your method is better than mine. ;)
Joe Farina
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Joined: Wed Jan 07, 2015 2:10 pm

harbor freight micrometer

Post by Joe Farina »

Since I use a type of puddling method (spread with a Mayer bar), I measured the bare glass adjacent to the coated area, and then the coating (no gelatin needed to be scraped away, although that would have worked also). It was a single coating of film (one for each of the bar sizes). This was pre-exposure thickness.

The plunger does rotate, but that doesn't seem to be a problem. It also has a ratcheting mechanism that is rotated to get the final reading (it applies a predetermined amount of force, so that the force used to get the final reading is constant in each case). I need to do a little more testing to see if this mechanism is helpful for DCG films, I just used a reasonable amount of pressure (without using the ratchet) and it seemed to work fine.

I recommend that anyone doing DCG get a decent micrometer, this one is certainly cheap, and it works, at least for the present ;)
Tony

harbor freight micrometer

Post by Tony »

A little off topic but does MBDCG better with thicker coatings?
You don't have to answer but DCG discussions has been on the boring side lately :cry:
Joe Farina
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Joined: Wed Jan 07, 2015 2:10 pm

harbor freight micrometer

Post by Joe Farina »

Film thickness in MBDCG (and regular DCG) opens up a lot of questions, and I got even more confused after following the "film thickness" thread. That's why I decided to use a variety of Mayer bars for my first tests. With a given winding on the bar (and a given gelatin concentration), the thickness should be quite repeatable. So far, I have tried the 14 and 17 micron coatings, and didn't see any difference (but that was only a 3 micron variation).

I constantly re-read my collection of papers on MBDCG looking for common observations by the authors. If the goal is to get a narrowband recording on MBDCG, then I get the impression that a thicker coating is favored, in the range of 18 to 25 microns. My objective is narrowband, because I'm working on two-color MBDCG. One paper by Rimpler et al. on MBDCG (SPIE 2333, "Influence of some parameters on grating structure and diffraction efficiency in red sensitive DCG") showed a relationship between diffraction efficiency and film thickness, with the thicker coatings being brighter than the thinner ones (around 25 microns appearing to be best, according to them). But of course there are a myriad of other variables involved such as gelatin type, MB concentration, hardening methods, etc.

Zhu and the others (who needed a narrowband result for full-color MBDCG) seem to prefer something in the 18 to 25 micron range, but they are not explicit about it, and I may try to duplicate their coating method to get a handle on how thick their coatings were. I would need to mix their exact film formula, and spread 8ml over an area 8 X 24 cm (this is what they specified) and let set by gravity. Then measure using a micrometer.

Not many papers discuss narrowband MBDCG except Zhu et al. One big difference between the Chinese formula and the original one by Blyth (and also Cristiano Perrucci's formula) is that it uses a much smaller amount of TMG, about 14% of what Blyth specifies. I'm assuming they used this smaller amount because they didn't want too much to wash out during processing, which would cause a color shift to the blue. Blyth states (and I certainly believe him) that more TMG causes better sensitivity, yet Zhu and the others claim very good sensitivity for their emulsion, 60mJ for 633, while Jeff's was said to be 50mJ. It's just possible they were getting good sensitivity due to the 18 micron film thickness, while I think Jeff's film was much thinner.
msxc
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Joined: Wed Jan 07, 2015 1:08 am

harbor freight micrometer

Post by msxc »

Hi Joe,

Hope to see some pictures of multicolor MBDCG:) Zhu article shows only one small pictures and this system seams to be very interesting.

Greetings,
msxc
Joe Farina
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Joined: Wed Jan 07, 2015 2:10 pm

harbor freight micrometer

Post by Joe Farina »

So far, I've done 5 exposures, and on the last two, at least there was some kind of result. Extremely feeble at this point. I exposed a flat aluminum plate with painted color squares (in contact with the emulsion) in Denisyuk mode. When I first looked at the image, all the colors looked gray. Then I put the hologram against a black background, lit it with a stong halogen light, and finally I could see some color variation. This emulsion batch isn't responding well (maybe it will improve with age) and the results are dim. I guess we've all been there ;)
msxc
Posts: 30
Joined: Wed Jan 07, 2015 1:08 am

harbor freight micrometer

Post by msxc »

Joe Farina wrote: This emulsion batch isn't responding well (maybe it will improve with age) and the results are dim. I guess we've all been there ;)
Have a fruitful experimentations then! Article by Zhu is very nice and interesting- follow up on this is material is exciting so I bet many readers will enjoy to see outcomes(I will!). :geek: :D

Fingers crossed,
msxc
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