"Blooming" of gelatin?

Overhardening can negate the effect of sizing.

PE

Hello to you all,

Could there be a standard, apart from Bloom, that describes the setting or coagulating properties of gelatin?
I simply can´t get the right emulsion viscosity for coating paper. It remains as fluid as water, adding more bloomed gelatin doe not have a positive effect.
I´ve been using photograde gelatin up to now, I am going to give foodgrade gelatin a try. Temperature at 40 Celsius.

Thanks for your help

Henk

Henk;

You are confusing the term "blooming" with Bloom Index or BI. Blooming is the act of softening gelatin with a small amount of water prior to addition to the emulsion. BI or Bloom Index refers to the coagulating properties and viscosity of the gelatin. Figures usually range from 75 BI to 250 BI or even 300 BI. Normal photo grade gelatin is about 250 BI and at about 5 - 10% will coat properly at about 40C - 45C. If there are too many salts left in the emulsion it will be more fluid, and it will be more fluid if there is Alcohol present.

Remember, coat film and plates on a surface that is hot and with the plate hot, but coat paper on a cold surface for best results. Make sure that your coating instrument of whatever kind is hot.

PE

Henk,

Try reducing the temperature of the emulsion for coating. I really think you should try that before you introduce other variables. I coat paper at 40C, but I coat film at 34C and plates at 37-38C. Adjusting temperature is a serious "trick of the trade."
d

fwiw, I don't pre-heat my coating tools no matter what I'm coating. If you do pre-heat, recognize that is a temperature variable that must be addressed with changes to emulsion temperature.

Denise,

Thanks, I won´t give up. No way. I just have to keep it simple. I had the idea of bying a heated car windscreen in Holland. A rear window I mean, flat, straight. One of my funny ideas.
I first try to sort out at which temperature the emulsion starts to set, then I´ll try to coat just above that temperature.
Apart from your video tutorial in a movie about George Eastman, you could very well see how the emulsion was of a thickish nature and was applied by the same puddle pusher technique a you showed.
I know there are other ways too, but I´ll keep that for anotherday.
Have a good time,

Henk

Hello PE

Thanks PE , I looked it up this Patent Thing of Oskar Bloom.

I just wondered if there could be quality differences not meant by this Bloom index. My Adox gelatin could differ from any other quality.
Thanks again for helping me on.

Henk

Henk;

Gelatin sets at 20C. That is its melting point in water, regardless of BI. However, on paper it appears to set even when warm, as the water is absorbed into the paper support. You can observe this because the wet melted gelatin is glossy, but as it absorbs into paper and begins to set, it becomes hazy or mildly matte in texture.

The Adox gelatin and paper appear to be very fine materials. I have tested the Baryta paper with good results. But, I use Kodak, Rousselot or Gelita gelatin here.

PE