Hello everyone!
Few days ago I succeeded in making my first holograms, but I still have some problems.
I work with a 445 nm diode laser (the famous projector diode) and home-made DCG plates (4g KDi, 12g culinary grade gelatin, 100ml water, veil coated). It is still difficult to make them, but I'm working on my veil coating skills, and I'll try to make a batch of mold coated plates tomorrow.
And now the problems:
First of all, most of my plates came out milky-white. I understand this happens because the gelatin is too soft. I tried hardening it with a 100w light bulb, but with almost no results. I tried hardening it after i rinsed it to remove the KDi with very low concentration bath of formaldehyde. I turned out crystal clear, but no hologram. So what should I do to remove that milkyness?
Another problem, is that most of them disappear when Itake the plate out of the last bath of isopropyl alcohol and blow-dry it. While it is in the alcohol bath i can see it, it is pretty bright, but when i start drying it, it disappears almost completely. Where the plate is milky, there still is some image,not as bright as it was in the alcohol, but where the plate is clear, there's no image at all. So, what should I do?
Thank you in advance!
Some newbie questions about DCG
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Joe Farina
- Posts: 805
- Joined: Wed Jan 07, 2015 2:10 pm
Some newbie questions about DCG
Hello Mihai and welcome to the forum.
I think your concentration of dichromate is too high. Try 3 grams dichromate, 30 grams gelatin, and 200 ml water. What I think is happening is that your holograms are shrinking and shifting into the uv, becoming invisible. Since your dichromate concentration is high, that extra solid material (dichromate) might be washing out of the emulsion, thus causing greater shrinkage. Since you're recording at 445nm, it can't shrink too much without going into the uv (or close to it). It seems that most holographers (including me) use ammonium dichromate, but I assume potassium is ok.
Milky DCG is caused by soft gelatin and/or higher temperature water baths or alcohols. The type of gelatin has a big influence on the final result. The Knox brand is standard for DCG in the US, but I don't know if there's an accepted standard in Europe. A fellow holographer in the Netherlands once had me send him a large quantity of Knox gelatin, so maybe the choice of gelatin is not so clear-cut in Europe compared to the US. Hopefully someone will chime in regarding the type of gelatin available in your country, which is good for DCG. The choice of gelatin is quite important, some culinary gelatin is quite soft, I think.
I would stay away from formaldehyde for hardening. Light can be used (such as your 100W bulb). I think heating can also be used. Most holographers seem to prefer fixer hardening (although I prefer the 100W bulb). You can also allow your plates to age, which will also cause them to harden due to the dark reaction. I store my plates in the refrigerator, and they seem to be optimum in about 30 days. I think they will harden quite quickly if not refrigerated (becoming too hard). If you're using warm or hot liquids (water or alcohol) you can try cool liquids instead.
I'm glad you're using the 445nm diode to make holograms. Please post any further questions.
I think your concentration of dichromate is too high. Try 3 grams dichromate, 30 grams gelatin, and 200 ml water. What I think is happening is that your holograms are shrinking and shifting into the uv, becoming invisible. Since your dichromate concentration is high, that extra solid material (dichromate) might be washing out of the emulsion, thus causing greater shrinkage. Since you're recording at 445nm, it can't shrink too much without going into the uv (or close to it). It seems that most holographers (including me) use ammonium dichromate, but I assume potassium is ok.
Milky DCG is caused by soft gelatin and/or higher temperature water baths or alcohols. The type of gelatin has a big influence on the final result. The Knox brand is standard for DCG in the US, but I don't know if there's an accepted standard in Europe. A fellow holographer in the Netherlands once had me send him a large quantity of Knox gelatin, so maybe the choice of gelatin is not so clear-cut in Europe compared to the US. Hopefully someone will chime in regarding the type of gelatin available in your country, which is good for DCG. The choice of gelatin is quite important, some culinary gelatin is quite soft, I think.
I would stay away from formaldehyde for hardening. Light can be used (such as your 100W bulb). I think heating can also be used. Most holographers seem to prefer fixer hardening (although I prefer the 100W bulb). You can also allow your plates to age, which will also cause them to harden due to the dark reaction. I store my plates in the refrigerator, and they seem to be optimum in about 30 days. I think they will harden quite quickly if not refrigerated (becoming too hard). If you're using warm or hot liquids (water or alcohol) you can try cool liquids instead.
I'm glad you're using the 445nm diode to make holograms. Please post any further questions.
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Kiffdino
Some newbie questions about DCG
gelatin I use in Germany is called, "Gelatia" 220 bloom ultra quality or something.
I havent tried the "knox" yet. I dont know whats available in romania.
Though i dont think the gelatin is your biggest issue at the moment.
DCG holograms that look great in alcohol, and later after drying not, This happens alot to me.
Actually my rule of thumb is, the better is see the hologram in the alcohol baths, the more milky the final hologram will be after drying.
But thats just me. Maybe im wrong on that.
After alot of bad plates i traced my milkyness problems back to my initial coating process. I dried my plates too fast. This caused moisture to get trapped in the lower parts of the gelatin, while the upper part was allready dry. So the gelatin stayed super soft in the lower parts and even drying the plate for days didnt fix it.
This soft gelatin gave me my milkyness.
Try to do your coatings at very high room humidity ( 90%+), then set them to dry and keep the humidity in your room high. Than gradually reduce humidity over the day to get back to normal.
I havent tried the "knox" yet. I dont know whats available in romania.
Though i dont think the gelatin is your biggest issue at the moment.
DCG holograms that look great in alcohol, and later after drying not, This happens alot to me.
Actually my rule of thumb is, the better is see the hologram in the alcohol baths, the more milky the final hologram will be after drying.
But thats just me. Maybe im wrong on that.
After alot of bad plates i traced my milkyness problems back to my initial coating process. I dried my plates too fast. This caused moisture to get trapped in the lower parts of the gelatin, while the upper part was allready dry. So the gelatin stayed super soft in the lower parts and even drying the plate for days didnt fix it.
This soft gelatin gave me my milkyness.
Try to do your coatings at very high room humidity ( 90%+), then set them to dry and keep the humidity in your room high. Than gradually reduce humidity over the day to get back to normal.
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Johnfp
Some newbie questions about DCG
Welcome Mihai,
Even though this is a beginner question, I believe it should be in the DCG section. Moderator???
Are you using a chemical fixer? Or just the light fixing? Fixing properly is a very important step.
If you are using light to fix, then cover half the plate and expose to the light. Then process. If you see no difference between the two sides, then you may need to expose to the light even more. You should see a big difference between the two side.
Other things to try other than what Joe and Kiffino have stated.
Longer exposure (probably about double). This would be my first easy correction to try as exposure hardens the emulsion also.
Exposose (harden) the plate with your light bulb before even shooting the hologram with the laser.
More alchol baths (Not sure what your are using but instead of lets say 50%, 100% use 35%, 50%, 70%, 90%, 100%) If you buy 70%, 90% and 100% alcohol, all concentrations are easy to make. Cut the 70% in half for 35. The 100 in half for 50, then 70 out of the bottle, 90% ot of bottle and 100% out of bottle.
Lower alcohol temperature for the last bath (and prior baths if you heat them)
Lower water temperature before the alcohol baths
The one thing I want to point out is that if you are getting a milky hologram, you are right on the very edge of getting a super bright hologram. Don't change too much, just change one thing a time.
Even though this is a beginner question, I believe it should be in the DCG section. Moderator???
Are you using a chemical fixer? Or just the light fixing? Fixing properly is a very important step.
If you are using light to fix, then cover half the plate and expose to the light. Then process. If you see no difference between the two sides, then you may need to expose to the light even more. You should see a big difference between the two side.
Other things to try other than what Joe and Kiffino have stated.
Longer exposure (probably about double). This would be my first easy correction to try as exposure hardens the emulsion also.
Exposose (harden) the plate with your light bulb before even shooting the hologram with the laser.
More alchol baths (Not sure what your are using but instead of lets say 50%, 100% use 35%, 50%, 70%, 90%, 100%) If you buy 70%, 90% and 100% alcohol, all concentrations are easy to make. Cut the 70% in half for 35. The 100 in half for 50, then 70 out of the bottle, 90% ot of bottle and 100% out of bottle.
Lower alcohol temperature for the last bath (and prior baths if you heat them)
Lower water temperature before the alcohol baths
The one thing I want to point out is that if you are getting a milky hologram, you are right on the very edge of getting a super bright hologram. Don't change too much, just change one thing a time.
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Joe Farina
- Posts: 805
- Joined: Wed Jan 07, 2015 2:10 pm
Some newbie questions about DCG
Yes, that's a good thing to try first.Johnfp wrote:Longer exposure (probably about double). This would be my first easy correction to try as exposure hardens the emulsion also.
Some newbie questions about DCG
Ah you guys are the best! i agree with every word above! Try to reprocess the milky holograms starting with the waterbath, heat the heck out of your last ALC bath and heat dry the plate as much as you can stand, and you may still have an image in there............................
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Mihai
Some newbie questions about DCG
Tank you all for your replies.
I've tried exposure from 2 minutes to 30 minutes, the longer exposures solved just a little bit the milkiness problem, but there was no image.
I've tried with more alcohol baths, one alcohol bath, warm alcohol, cool alcohol, etc., but the results were the same: a really milky hologram, or no image at all.
I haven't tried light hardening the plates before the exposure, i will give it a try.
In the meantime, I bought four different kinds of gelatin and tested their hardness by swelling the same amount of gelatin in cold water, and weighting it afterwards. It turned out that the gelatin I was using was pretty soft. So, I made a new batch with the hardest gelatin that I have, with less dichromate as Joe pointed out, and gave it a shot. The results were quite good! Now i have the first transparent plate that has a hologram on it!!!
Thank you very much guys!!
I will post some pictures in a day or two (all my photo gear is somewhere 300km away right now), and probably I will post also a lot of other questions.
I've tried exposure from 2 minutes to 30 minutes, the longer exposures solved just a little bit the milkiness problem, but there was no image.
I've tried with more alcohol baths, one alcohol bath, warm alcohol, cool alcohol, etc., but the results were the same: a really milky hologram, or no image at all.
I haven't tried light hardening the plates before the exposure, i will give it a try.
In the meantime, I bought four different kinds of gelatin and tested their hardness by swelling the same amount of gelatin in cold water, and weighting it afterwards. It turned out that the gelatin I was using was pretty soft. So, I made a new batch with the hardest gelatin that I have, with less dichromate as Joe pointed out, and gave it a shot. The results were quite good! Now i have the first transparent plate that has a hologram on it!!!
Thank you very much guys!!
I will post some pictures in a day or two (all my photo gear is somewhere 300km away right now), and probably I will post also a lot of other questions.
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Joe Farina
- Posts: 805
- Joined: Wed Jan 07, 2015 2:10 pm
Some newbie questions about DCG
That's an interesting way of testing hardness. Could you please elaborate on it? I assume that, since hard gelatin swells less compared to soft gelatin, less water is absorbed. Thus for an equal number of grams of gelatin, the "swelled mass" which weighs the least is the hardest gelatin. Do you keep the amount of swelling time constant for each sample, and do you have to "skim" the excess water from the top of the container before weighing it?Mihai wrote:In the meantime, I bought four different kinds of gelatin and tested their hardness by swelling the same amount of gelatin in cold water, and weighting it afterwards. It turned out that the gelatin I was using was pretty soft.
Nice job with your hologram by the way
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Martin
Some newbie questions about DCG
I would try to "tinker" around the temperature of your water (= "swelling") bath. Most of the time I was doing a couple of methods of gelatin sensitization (dichromated, ferric, several types of monomer, occasionally even AgX), I used to do it with culinary gelatin. Controlling the temperature of the swelling bath seems to be of utmost importance for soft gelatin like this. Depending on the kind of sensitization, exposure levels etc. the optimum may be anything from 15 - 35°C. The range of tolerance from getting no hologram at all to a noisy, milky one may be very narrow: So setting the temperature of your swelling bath at say, 15°C may be a good start...Mihai wrote:Hello everyone!
Few days ago I succeeded in making my first holograms, but I still have some problems.
I work with a 445 nm diode laser (the famous projector diode) and home-made DCG plates (4g KDi, 12g culinary grade gelatin, 100ml water, veil coated). It is still difficult to make them, but I'm working on my veil coating skills, and I'll try to make a batch of mold coated plates tomorrow.
And now the problems:
First of all, most of my plates came out milky-white. I understand this happens because the gelatin is too soft. I tried hardening it with a 100w light bulb, but with almost no results. I tried hardening it after i rinsed it to remove the KDi with very low concentration bath of formaldehyde. I turned out crystal clear, but no hologram. So what should I do to remove that milkyness?