Sparkly stuff in gelatin sizing
I have just begun experimenting with sizing papers with gelatin. Upon drying, I see minute sparkly things embedded in the gelatin, which show through in the final prints (cyanotype and Van Dyke Brown). The sparkly stuff shows through clearly and seem to act as a resist to the sensitizer coating.
Anyone know what these things are made of? Can they be filtered out somewhere down the process of preparing the gelatin?
I am using an experimental dilution of 1 packet Knox gelatin (7 g.) to 500ml distilled water. I find that the dilution is viscuous enough for sizing, but not so thick that the gelatin sets in the container.
Any information will be helpful.
Originally Posted by dmax
First, you have "sparkles" which are grains of undisolved gelatin. To help dissolve the gelatin better always let the gelatin bloom and dissolve before heating.
Second add about 50 ml of grain alcohol for a half liter solution of gelatin. This will aid in dissolving the gelatin.
Third if you are going to gelatin size, use a about a 3% solution of gelatin.
Fourth, always weight the gelatin in the packets as there may not be the quantity of gelatin marked on the packs.
Fifth, you don't mention why you are sizing paper for these processes to begin with. Normally for VDB or cyanotype you don't need to gelatin size if you are using a "good" paper. Why do the extra work if you don't need to?
Knox unflavored gelatin also contains a silicate dessicant (IIRC) and a few other ingredients to make it more palatable and 'easy to dissolve'.
It would be best to use photo grade gelatin for this purpose than food grade gelatin. The photo grade gelatins are much more highly purified and have no additives. Use 175 bloom or higher.
Look on the side of the package for the extra ingredients in the Knox gelatin.
I have to both agree and disagree with Don. I don't think the sparklies are caused by undissolved grains of gelatin. I've let the gelatin bloom as long as overnight and still get them. My impression is that they are caused by the somewhat bubbly and viscous nature of the gelatin when it's dissolved and heated. I definitely agree that adding grain alcohol will help reduce or eliminate them. I add Everclear at a rate of about 15:1 gelatin solution to alcohol. I think this reduces the sparklies because the alcohol reduced the propensity of the gelatin to create bubbles and also reduces the viscosity a bit at the same time. I've used both 250 bloom gelatin as well as deionized ossein from B&S. I usually make the gelatin at a 3% or 4% strength for gum printing.
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I use a 13g packet of food gelatine to 500ml water. I let it bloom for 1/2 hour or so in cold water then use a bain marie and bring it up to 60-70 deg C adding 50ml methanol. Hardener (formaldehyde) goes in just before I size. I coat with a foam brush. I only get sparklies on the outside edge, where sized and unsized paper meet.
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I've coated at up to 10% gelatin with no alcohol, and have had no such problem.
I use photograde 250 bloom gelatin from two sources. I make my gelatin up as we did at EK as a 20% wt/wt solution. I add 20 g of gelatin to 90 g of water at room temp with constant stirring to keep lumps from forming. I heat the mixture to 60 deg C and hold there for about 1 hour with gentle stirring and then add 1 drop of 10% thymol and chill set.
When ready for use, I dilute by weight to the percent I want with water and melt and coat.
I have coated at up to 1000 mg/sq ft on many different papers and on film support with no problem.
As a check for my methodology, I use 2 grams each of R, G and B food dyes in 120 grams of 10% gelatin and coat this on paper support to test coating and paper parameters.