View Full Version : Adhesion to glass plates.

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10-06-2008, 06:42 AM
I noticed that some people regularly have trouble with allowing gelatin to stay on the glass during processing.
Here is a trick that will really make gelatin stick to the glass strongly even when using the most alkaline developers. Even unhardened gelatin will stay on the glass easily.

1] Make a stock solution of:
-- 4ml 3-amino-propyltriethoxysilane (CAS#: 919-30-2)
-- 5.5ml of Isopropyl Alcohol
-- 0.5ml De-Ionized Water
-- Allow this solution to sit for 24 hours
2] Clean your glass plates well, first with dishwashing liquid and then with a Ammonia based glass cleaner (called Glassex here in Holland)
3] Take 1ml of the solution made in step 1 and add 20ml of Isopropyl Alcohol to that.
4] With a clean paper towel rub this solution onto your freshly cleaned glass plates. You will see a white haze appear on the surface of the glass.
5] Let the plates sit for a few hours to allow the silane to bond to the glass.
6] Remove the haze from the glass with an ammonia based glass cleaner. (This becomes difficult if you wait more than about four hours)
7] Your plates can now be stored until the time you are ready to coat them.

When using this procedure you will not need to pre-sub the plates with chrome hardened gelatin before coating.

(Please mix your Silane in a well ventilated area because it is not a very pleasant liquid. Wear eye protection and gloves. When using it, I wear a painters mask with a carbon filter.)

10-06-2008, 07:05 AM
Oh, one thing I forgot to mention: The stock solution made in step [1] is good for about a week and should be discarded after that. The diluted solution made in step [4] is good for one day. So, it is a good idea to prepare a good stack of glass when you do this procedure.

Happy photographing. :)

Kirk Keyes
10-06-2008, 12:53 PM
Hans - can you recommend a source for the Silane? That's probably not going to be an easy one for most people to get ahold of.

Also, it's pretty corrosive stuff. I'm glad you mentioned the safety precautions.

10-06-2008, 01:22 PM

Bostick & Sullivan carries silane.


Kirk Keyes
10-06-2008, 01:34 PM
Joe - Thanks. I guess I should check out the other supplies they carry too.

Kirk Keyes
10-06-2008, 01:45 PM
Joe - do you know what strength B&S recommend using it at?

Nicholas Lindan
10-06-2008, 01:57 PM

This may be the magic ingredient in the American product "Rain-X Anti-Fog" or "Fog-X", a treatment that makes glass hydrophillic. There is also the complimentary product "Rain-X" (without "anti-fog" in the name) that makes glass hydrophobic.

Fog-X works very well on camera eyepieces.


Struan Gray
10-06-2008, 02:14 PM
The amino-terminated version is hydrophilic. Hydrophobic coatings can be made using flourinated alkane chains, although the ones I am familiar with are longer than this one (12 or 13 carbon atoms instead of 3).

The bonding reaction evolves HCl, which can be a problem in some environments. Probably not a biggie in this application, but make sure your containers and any fume-extraction system can handle acids.

"Self-assembled monolayers" is the buzz-phase of the day if anyone wants to look the details up.

Struan Gray
10-06-2008, 02:26 PM
PS: I know that here in the lab we maintain higher safety and quality standards than a hobbiest working with dilute solutions, but silane treatment seems a bit too much of a hassle just to prepare a glass surface for gelatin deposition. For really good silane layers you need to carefully control both water and oxygen in the local environment, and the method proposed here does neither.

Indium-tin-oxide is nicely hydrophilic, and widely available as a coating on float glass for window panes and patio doors. I would investigate that as an alternate substrate before getting my hands dirty with silane.

10-06-2008, 03:17 PM
For holography we use the silane all the time. It works great. Another holography trick to make a really good coating is to treat one piece of glass with silane. Then treat another piece of glass with Rain-X to make it really hydrophobic. Put on each edge of the Rain-X treated glass a strip of Scotch tape. Warm both plates with a hair drier and put a puddle of emulsion on one of them (emulsion with about 12% of gelatin). Put the other piece of glass on top of it and put this sandwich in the fridge for about two hours and then carefully separate them. The gelatin will stay on the silane treated plate and be perfectly flat. It will need about one hour to dry and is ready for use.

10-06-2008, 03:18 PM
p.s. the Rain-X you need for the above trick is the one that makes the glass hydrophobic. The one that you use on the outside of the car.

10-06-2008, 03:19 PM
This may be the magic ingredient in the American product "Rain-X Anti-Fog" or "Fog-X", a treatment that makes glass hydrophillic.
I have tried this. Did not work.

10-06-2008, 03:20 PM
Hans - can you recommend a source for the Silane? That's probably not going to be an easy one for most people to get ahold of.
SigmaAldrich has it. I order mine here in Holland from a chemistry supplier that sells to schools and universities.

10-06-2008, 03:25 PM
It is my experience that emulsion slips off the glass far more easily if a hardener has been added. For frill-free coatings: forgo hardeners, use Everclear as the only surfactant, and have very smooth edges on your plates. Clean the glass well and end with a rinse of half Everclear, half distilled water - all very simple with a minimum of toxic chemicals, time and expense.

Kirk Keyes
10-06-2008, 07:07 PM
Intersting Denise - with my limited plate pouring I had little frilling. I used chrome alum and I ground the edges of my plates.

I know I've asked before, but were you using glyoxal or chrome alum for the hardener?

Kirk Keyes
10-06-2008, 07:08 PM
Hans - are you making holo plates for professional research or for fun? I guess I'm interested in your background...

10-07-2008, 07:01 AM
Hans - are you making holo plates for professional research or for fun? I guess I'm interested in your background...
At the moment just for fun.

Photo Engineer
10-07-2008, 10:30 AM
Glyoxal allows more frilling and blistering on glass plates than chrome alum. Grinding the edges of your plates with a file or some emory paper to give a tiny rough edge will decrease frilling. You can use a mixture of chrome alum and glyoxal. Chrome alum is slower to harden than glyoxal. It is so slow, that you can find old formulas in which the emulsion was prepared for coating with the chrome alum and then stored for a few days in the cooler. This cannot be done with other hardeners.

Both chrome alum and glyoxal decompose with keeping and lose activity. Both can react with some addenda in emulsions that decrease or increase activity, and both are sensitive to pH.


10-07-2008, 11:37 AM

I only use a hardener (glyoxal) when I'm doing emulsion transfers. The emulsion slips right off the substrate in a perfect, transferable sheet. I discovered this by way of my usual research s.o.p. I always start a new recipe with as few additional chemicals as possible, and then add one at a time to determine the pluses and minuses of each addition. My original dry plates without hardener were great, but due diligence had me try glyoxal. Voila! the emulsion transfer was born. But, since I rarely want an emulsion transfer, I never use hardeners in my dry plate recipes.

Chrome alum was almost certainly added to the old dry plates to protect them against a range of water temperatures. Before refrigeration and air conditioning, photographers had a big problem during the summer months. Today, we don't need that insurance. Glyoxal is a great hardener for paper, but a dismal failure for plates. In addition, chrome-hardened plates should cure for up to a week. That is time I don't want to expend and in that time the chances of fogging go up. I recommend that you go without a hardener and watch your water temperature and plate handling protocol (don't manhandle the edges while the plates are wet.) K.I.S.S.

One more tip: Emulsion will have a tendency to pull back from an edge defect on the glass. Raw snapped glass has a sharp edge that will cut the emulsion. It is important to smooth the edges of the plates before coating. This allows the emulsion to flow over the edges and dry without flaws that can break during development and allow the chemistry to work its way between the emulsion and glass (i.e. 'frilling').

Welcome to APUG! I can hardly wait to see your holograms.


10-07-2008, 12:47 PM
Hi Everyone,
Befor going out to buy exotic chemicals, read my article on Glass preparation on The Light Farm. Using this procedure, I NEVER see frilling or lifting of the emulsion from glass, hardener or none.
I have been using amino-silane for adhesion to glass since 1974. We used to buy it by the 55 gallon drum. It works much better if you can incorperate it into the emulsion,rather than coat it directly onto the glass.
A.freind of mine uses amino-silane to attache Carbon Tissue,which is gelatin based, to glass.
Counter-intuitivly, his best results are obtained by applying 4 heavy coats of 5% amino-silane to glass and not polishing.
I purchase my amino-silane from HIS Glassworks. They have a website and sell 5% amino -silane in "ultra-pure" IPA for $33.00/liter. It is important to keep the silane solution water free prior to coating.