When I use a dropper to mix my coating solution, I notes that the dropper would make 20 drops of Ferric oxalate with one load... and with palladium it would only make 10 drops! The palladium is dens comparing with Ferric oxalate!! wouldn't that going to miss-measuring the coating solution? What I mean is that 20 drops of palladium is much bigger than 20 drops of ferric oxalate.
Please tell me if that normal or what
Thank you in advance
Nasser
I have not notice such a large difference. Are you using different droppers for each solution?
I suggest buying several droppers, and using water, pick the droppers that deliver the same amount (try 20 or more drops into a graduated cylinder to check amounts).
Be consistent in how you hold the droppers (same angle, same amount of time between drops when squeezing the bulb, etc).
Good luck!
The droppers often vary in the drop size, and that does affect the 'ideal' mixture ratios, so I carefully test them to get a sense for how many drops per ml.
Then, I promptly forget that and just do it by feel for the most part. Since most larger prints are a full dropper anyway (or more), it's not logical to be counting drops. For small prints, counting drops makes sense, so just figure out a process to calibrate the amounts of drops with each dropper to give you the amount you want.
The way that Vaughn recommends is the way I did it to get a consistent result.
---Michael
What kind of droppers are you using?
To prevent contamination of your chemicals, you should have a dropper dedicated to each chemical. Using the same dropper on all chemicals is a bad practice!
One of the things that you learn in Pt/Pd printing is that there is a lot of science behind droppers. A key point is that you want a set of droppers that are consistent - the volume of each drop is not important because you will eventually calibrate your process to arrive at the number of drops you need, but you want each drop to always have the same volume. Unfortunately, glass droppers are made by blowing, and that means that there is a lot of variation between droppers. The only way to get consistency is to use droppers that are made using an extrusion/molding process - and that means plastic droppers. Plastic may sound inferior, and potentially problematic, but the fact is that plastic is ideal, especially if you have dedicated droppers for each chemical.
B&S sell a line of droppers (and bottles with dropper closures) that are very consistent.
I've tested the B&S plastic droppers and they are very consistent. Each drop will have a volume of about 0.05 ml. Yes the different solutions will have different SG but if we measure by volume with drops then using plastic droppers will be consistent.Originally Posted by Louie Powell
Always test for yourself.
As MM points out, for large prints counting drops isn't practical and is error prone. Disposable plastic pipettes can be purchased from The Chemistrystore.com and they work very well for larger volumes. I also dispense into glass shot glasses which can be rinsed and reused and offer a heavy stable container to dispense to.
Good luck,
Don Bryant
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