making a uniform size drop of ink?

[deleted-3443]

My daughter (5th grade) wants to test how well some handmade paper takes ink. She is having a hard time coming up with a way to put the same amount of ink on a piece of paper every time.

Since we can't trust our dropper, I'm wondering if there is a higher-quality dropper I could buy? Or, should we try another device for applying ink -- but pen and paintbrush are hard to do consistently, too.

She also tried just dipping the end of the paper in the ink to see how far it moved, but the unsized paper absorbed the ink very fast, and kept changing as she tried to measure, then the whole strip was soaked.

--Janet

[audreyln]

Janet,

It sounds like you are your daughter have already done a really great job of troubleshooting your issue. A commercial pen or a new dropper might give you the most consistent results. As you said, purchasing a new dropper (try looking for a volumetric pipet) or maybe even a small syringe might work well.

Good luck and have fun!

Audrey

[deleted-71588]

Droppers aren't ever going to be accurate for different liquids.

Typically people using droppers or pipettes for experiments have to calibrate the drops for each liquid they use by counting how many drops it takes to fill/empty some graduated cylinder and then divide the number of ml by the number of drops to determine the per drop volume for that liquid.

A quill pen, calligraphy pen, dry fountain pen, empty ink cartridge pen, or other writing "nib" style pen that uses capillary action between two prongs when dipped consistently to some mark approximately 1/8 of an inch up the nib will hold a fairly consistent amount of ink if you touch the top and bottom surfaces to the top of a glass ink well so that only the ink on the nib and in the split are left.

A microliter syringe - think diabetic supplies at your local pharmacy is another option; however, dispensing very small amounts accurately is more difficult so you might have to adapt your experiment to deal with a larger but more consistent volume of ink if you go with a syringe. In any case, you want the smallest diameter syringe you can find.

[deleted-3443]

Thanks for the replies. We'll check at the pharmacy and art supply store and see what we can come up with.

--Janet