coating help needed

Dichromated Gelatin.
ahgu
Posts: 23
Joined: Tue Dec 08, 2015 11:30 am

coating help needed

Post by ahgu » Wed Jul 11, 2018 2:11 pm

I don't know how Rallisson did his pin coating. I cannot get uniform coating with DCG. See picture below.

solution about 5-25-120. Temp 40-50C. veil coat it first then spin at 80RPM Under regular light, it is very obvious it is not even.

coating2.jpg
coating2.jpg (155.87 KiB) Viewed 2857 times
I also tried mold coating. Looks good until developing, Get those circular flow pattern left after developing. Shim is about 50um. Final dried thickness about 7-8um thick.
coating3.jpg
coating3.jpg (160.34 KiB) Viewed 2857 times
Also tried Meyer bar, first try left thread mark, heat it up, no more thread mark, but uneven.

DCG solution is pretty thick even at 50C, it is very resistant to flow. I wonder how you guys get it to flow uniformly.
Last edited by ahgu on Thu Jul 12, 2018 11:27 am, edited 1 time in total.

ahgu
Posts: 23
Joined: Tue Dec 08, 2015 11:30 am

Re: coating help needed

Post by ahgu » Wed Jul 11, 2018 2:17 pm

The white is another issue. I suspect the cause was
1. the solution was not overnighted.
2. Did not wash out all the D after fixer.

I suspect 1 might be main cause. The gelatin needs time to form better bonds. Correct me if wrong.

holomaker
Posts: 672
Joined: Wed Jan 07, 2015 8:01 am

Re: coating help needed

Post by holomaker » Thu Jul 12, 2018 7:00 am

When mold coating do not force dry it at all, otherwise
You may be sealing in moisture, don’t heat plates prior
To coating more than “just warm”, what thickness
Shim are u using , possibly films to thick to harden through out causing milky....

ahgu
Posts: 23
Joined: Tue Dec 08, 2015 11:30 am

Re: coating help needed

Post by ahgu » Thu Jul 12, 2018 11:22 am

Shim is about 50um. Final dried thickness about 7-8um thick.

What is the cause of the whiteness after developing? I don't get this with high bloom GEL , but get it with this type of 214 , 29.6mp viscosity, 5.3ph gelatin.

ahgu
Posts: 23
Joined: Tue Dec 08, 2015 11:30 am

Re: coating help needed

Post by ahgu » Sun Jul 15, 2018 10:10 am

http://www.holographyforum.org/data/pdf ... tation.pdf

Anyone how the idea behind this coater?
coat.PNG
coat.PNG (671.69 KiB) Viewed 2812 times

Steven
Posts: 32
Joined: Sat Jan 31, 2015 8:14 pm
Location: Cornwall, UK

Re: coating help needed

Post by Steven » Mon Jul 16, 2018 9:53 pm

ahgu wrote:
Sun Jul 15, 2018 10:10 am
Anyone how the idea behind this coater?
coat.PNG
Hi ahgu, I suspect that it is using a Doctor Blade. Something like this:
https://www.youtube.com/watch?v=f0OfjqKQwXg

Steven.
Success through failure - the amateur DCG holographer's path to enlightenment.

Martin
Posts: 82
Joined: Sat Apr 04, 2015 2:36 am

Re: coating help needed

Post by Martin » Tue Jul 17, 2018 3:24 am

Steven wrote:
Mon Jul 16, 2018 9:53 pm
ahgu wrote:
Sun Jul 15, 2018 10:10 am
Anyone how the idea behind this coater?
coat.PNG
Hi ahgu, I suspect that it is using a Doctor Blade. Something like this:
https://www.youtube.com/watch?v=f0OfjqKQwXg

Steven.
I think it's based on some kind of curtain coating (http://holotec.de/Produkte_und_Dienstle ... index2.htm).

Steven
Posts: 32
Joined: Sat Jan 31, 2015 8:14 pm
Location: Cornwall, UK

Re: coating help needed

Post by Steven » Tue Jul 17, 2018 7:01 am


I think it's based on some kind of curtain coating (http://holotec.de/Produkte_und_Dienstle ... index2.htm).
I think you must be right. Film thickness is dependant on coating speed.
Success through failure - the amateur DCG holographer's path to enlightenment.

ahgu
Posts: 23
Joined: Tue Dec 08, 2015 11:30 am

Re: coating help needed

Post by ahgu » Sun Jul 22, 2018 11:06 am

Martin wrote:
Tue Jul 17, 2018 3:24 am
Steven wrote:
Mon Jul 16, 2018 9:53 pm
ahgu wrote:
Sun Jul 15, 2018 10:10 am
Anyone how the idea behind this coater?
coat.PNG
Hi ahgu, I suspect that it is using a Doctor Blade. Something like this:
https://www.youtube.com/watch?v=f0OfjqKQwXg

Steven.
I think it's based on some kind of curtain coating (http://holotec.de/Produkte_und_Dienstle ... index2.htm).
Curtain coating requires gravity. This equipment is on a flat glass bed. I suspect it is some sort of blade.

holomaker
Posts: 672
Joined: Wed Jan 07, 2015 8:01 am

Re: coating help needed

Post by holomaker » Wed Oct 10, 2018 6:18 am

Spin coating needs a larger plate than you are using , 80rpm is not enough, either spin larger plates or spin the tiny plate faster !

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