First DCG, Please, Help me find the problem.

This is a forum to share experiences and ideas about holography.
JohnFP

First DCG, Please, Help me find the problem.

Post by JohnFP » Wed Feb 25, 2009 9:03 pm

The only movement you have to worry about is the object to plate in a Single Beam Reflection. So if you pick an object that you can lay the plate on top of, you won't have to worry about movement no matter how long your exposure.

Here is the best method.
http://holograms3d.com/Illustrations/SImpleSingle.jpg

In a single beam reflection the plate is actually the beam splitter. You don't have to worry about movement (other then allignment) prior to the beam splitter thus prior to the plate in a SBR. This short video proves it.
http://holograms3d.com/Test_Research/Fr ... riorBS.avi

You can find this movie on this page under the title "Proving Fringe Stability with Laser off Table "
http://holograms3d.com/Test_Research/Test_Research.htm

PS: If you try my method, which is actually the one Dave and most holographers use, don't forget to take note that we do not use the quartz halogen light for anything other then lighting the hologram when it is being blown dry to see the image come out. I pointed this out in the post before your last one.

Kiffdino

First DCG, Please, Help me find the problem.

Post by Kiffdino » Wed Feb 25, 2009 10:33 pm

A thankyou John, i didnt know that. My setup is actually almost like the one you described. Just that its upside down. The beam is coming from below with a mirror at brewster angle. Its the setup with a frame described in saxbys book.

Got to ask again, there is absolutely no difference between coating the glassplate with dichromate-gelatin-mix in the first place or
doing a gelatin coating first and then later on (after 12 hours) sensetizing it with dichromate . You get equal results ?
Joe Farina:
It's not necessary to use G307 if the objective is to coat plates with gelatin and no dichromate. The coated gelatin plates can be soaked in a dichromate solution later. Also, fixer is not necessary when usuing regular DCG. A 100W light bulb can be used instead.
I dont want to question Joe's expertise. But if the results are truely the same i would prefer doing the gelatin coating first and later on sensetization.
I just want to limit the stuff that gets into contact with dichromate. -we had that discussion before :D -

JohnFP

First DCG, Please, Help me find the problem.

Post by JohnFP » Wed Feb 25, 2009 11:25 pm

You and Joe are absolutely correct. There is not difference in coating plain gelatin and then sensitizing later. In fact, there are some benifits to doing it that way. One, you can use full lighting to coat plain gelatin, which helps do it more correctly. And secondly, plain gelatin plates will keep much much longer in the fridge then sensitized plate. And thirdly, as you expressed, you can coat with 0 AmDi, so this open up regular living areas to coat (bathroom, kitchen, etc.) Just be sure not to use anything you use with sensitized plates in the process (trays, tools, etc.).

One note: I am not sure how the maturity acts with the post sensitizing the plates. I know the gelatin would be fully cured but there would be no "dark reaction" crosslinking for additional hardening prior to exposing. So after you sensitize a plate with AmDi, and wipe the back off, and wait for it to dry (including setting time) for 10 or 15 minutes you will need to try to expose and process it to see how it acts (as young or old film). If it acts too young (milky white) then simply let it set longer before exposure or expose it to that quartz halogen light for a few minutes and it should age quickly or you could expose it longer. You may have to test how long it needs under the light.

I have never tried it but I wonder if a little photo flo or wetting agent (clear dish soap) in the AmDi solution would help reduce spotting on the emulsion side after sensitizing. I just gave it a sharp tap to knock the droplets off the emulsion side.

Kiffdino

First DCG, Please, Help me find the problem.

Post by Kiffdino » Mon Mar 02, 2009 2:47 pm

hi,
tried the dichromate only with fixer processing yesterday night.
sorry the object is again the coins, gets kinda borring but its the simplest thing :D
the hologram has about the same brightness as the g307-holograms i did before.
But theres still room for optimization. The plate is still milky.

So heres what i did:
-veil coating
-12 hours later sensetization with potassium dichromate
-drybox for 90 min
-exposure 80 sec
-dark 5 min
-fixer Tetetenal Superfix ( high strength, so 1+3 , 1 part fixer, 3 parts water, so thats 25% ) for 30 sec
-1st waterbath 60 sec
-2nd waterbath + two drops of handwashing soap,60 sec
-70% alcohol for 30sec, 90% for 30 sec / 100% for 45 sec then i saw deffraction + 15 sec so thats 1 min
last bath was heated to about 40°C
-5 min drying

thankyou for all the help so far
here are the pictures, all from the same hologram at different angles.
Attachments
three.jpg
three.jpg (69.67 KiB) Viewed 4712 times
two.jpg
two.jpg (73.45 KiB) Viewed 4713 times
one.jpg
one.jpg (68.56 KiB) Viewed 4713 times

dave battin

First DCG, Please, Help me find the problem.

Post by dave battin » Mon Mar 02, 2009 3:40 pm

Looks like you are underexposed (the red/brown color) and try a longer fixing time to reduce the milkyness. Now your work is ahead of you ! test, test, test ......................

Kiffdino

First DCG, Please, Help me find the problem.

Post by Kiffdino » Mon Mar 02, 2009 4:14 pm

hi Dave,
could you recomend some spefic times?
Im gonna shoot tomorrow again i guess.
How about fixing time 40 seconds and exposure 120sec 160 sec ?

Joe Farina

First DCG, Please, Help me find the problem.

Post by Joe Farina » Mon Mar 02, 2009 4:25 pm

Nice job, the middle photo looks especially good. As Dave said, now comes the tough part, improving the results little by little.

There was an interesting paper published in the Journal of Physics E: Scientific Instruments, Vol. 20 (1987) called "Reduction of sensitiser concentration gradients in dichromated gelatin films" by Jacobs and Marsland.

They did the gelatin coatings first, hardened them somewhat using a "photographic hardener" then soaked the plates in a 4% ammonium dichromate solution (with an added wetting agent) for 4 minutes, then dried overnight (horizontally).

The objective of the paper was to reduce the "sensitizer gradients" or irregularities which occur when draining the plates of AmDi/wetting agent, while in the vertical position (and before the overnight final drying).

To make a long story short, they said the plates should not drain for more than 5 minutes in the vertical position. For some reason, longer draining periods would result in irregularities, i.e., "sensitizer concentration gradients."

By the way, this is the only paper I know of which describes the "brush" method for coating gelatin on glass. They used a camel-hair brush to spread the gelatin out, then let it level out while in the horizontal position.

dave battin

First DCG, Please, Help me find the problem.

Post by dave battin » Mon Mar 02, 2009 6:18 pm

Kiffdino wrote:hi Dave,
could you recomend some spefic times?
Im gonna shoot tomorrow again i guess.
How about fixing time 40 seconds and exposure 120sec 160 sec ?
now you need to think ahead , take your exposed plate and cut it into four pieces and vary the procedure accordingly. as you play with it you will begin to understand it more...... i have never used the fixer you are using so i will not comment on time required, you need to discover this on you own now, its like going solo on you first flight!good luck!

again you may want to add a small ammount of that soapy water to the sensitising bath to lessen the dripmarks left from the dip step,(that is why i like to coat w/dichromate and gelatin together).

Kiffdino

First DCG, Please, Help me find the problem.

Post by Kiffdino » Fri Mar 06, 2009 3:37 pm

last night was a disappointment :(
i put some handwashing gel-soap in the dichromate sensetizing bath,
sensetized for 30sec, let the plate rest for 10 min in a cool spot and put it in a drying box for 90min.
Well when i took it out it looked like this.
What happened? I guess i got the wrong soap.
I think ill take a break now...
gonna learn some mold coating, get a new appartment, build a lab...
and then do the coating with gelatin AND dichromate from the beginning on in a perfect working environment.
see you then...
Attachments
DCG + soap.jpg
DCG + soap.jpg (152.43 KiB) Viewed 4854 times

Dutchelm05

First DCG, Please, Help me find the problem.

Post by Dutchelm05 » Fri Mar 06, 2009 4:11 pm

This looks like a case of over stauration. What percentage of AmDi did you use?
I've done this before with I think 7% AmDi, there could be a temperature element as well, is it still cold over there?
Hang in there kiffdino, you'll get it.

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