# Help identifying a length for this paper edge

• member 428835
In summary, the conversation revolves around an experiment conducted in late 2020 aboard the ISS involving water droplets. The exact size of the droplets is unknown and the individual is trying to back out a length scale, but is facing challenges with different metrics not agreeing with each other. They are also trying to determine the size of corrugated "jagged triangles" on a paper towel being used to dry the surface, potentially using the number of teeth per inch as a reference. There is a suggestion to include a measurement scale in future experiments and to check public restrooms for paper towels with similar serrated cuts. NASA's knowledge of the materials present on the ISS is also mentioned. The individual is seeking advice on how to obtain more information
member 428835
Hi PF!

Two years ago my lab launched experiments aboard the ISS. The experiment was simple: place two water droplets on a substrate, set camera above the drops, and watch them coalesce. However, the exact size of the drops is unknown (approximately 1 cm radii, though this number is debated). So I'm analyzing this data and have done A TON of work to try and back out a length scale, but no two metrics agree within 5% of each other, so I'm not overly confident. Now I may have to scrap the entire project, but before I do, this might be the key: does anyone know the size of the corrugated "jagged triangles" at the end of this wipe being used to dry the surface? An astronaut is holding it, and the drop is total about 20 mL volume (few cm long) to give you a guess.

Edit: I just found something and I THINK each triangle base might be 15/37 = 0.405 cm. But let me know what you think.

How could we possibly be able to answer this? Ask the astronaut.

But in the future, put a measurement scale in the experiment and record the specs/dimensions of the camera.

Wrichik Basu, robphy and BillTre
If that is a standard three panel brown paper towel, then (as far as I know) all use the same number of teeth per inch. It's called a serrated cut, and was the standard cutoff on towel folders up to about 15-20 years ago. Check out the local public restrooms for paper towels. You might get lucky.

The industry got away from serrated cutoffs because newer, tougher towel material is difficult to cut using serrated cutoffs. Much of my engineering career was working with cutoff systems.

member 428835
russ_watters said:
How could we possibly be able to answer this? Ask the astronaut.

But in the future, put a measurement scale in the experiment and record the specs/dimensions of the camera.
I wasn't in the control room. Wasn't even supposed to be my experiment, but my advisor sadly passed away, leaving the project for me to handle.

But regarding how to answer this: I think I found a solution so...

jrmichler said:
If that is a standard three panel brown paper towel, then (as far as I know) all use the same number of teeth per inch. It's called a serrated cut, and was the standard cutoff on towel folders up to about 15-20 years ago. Check out the local public restrooms for paper towels. You might get lucky.

The industry got away from serrated cutoffs because newer, tougher towel material is difficult to cut using serrated cutoffs. Much of my engineering career was working with cutoff systems.
This is helpful! What do you think of this?

Okay, so I'm pretty sure the triangle bases are 4,5, or 6 mm long. Like, 100% sure, but which...

You said no two methods agree within 5% of each other, but if they all agree within 15% of each other, you can figure it out by process of elimination

Any reason you can't show us any other pics? You've got enough video to do your experiment, so you can get more pics, but maybe we'll see something in them that you've missed.

I find it hard to believe NASA doesn't know what exact materials were present on/available on/sent to ISS.

Wrichik Basu and BillTre
Borek said:
I find it hard to believe NASA doesn't know what exact materials were present on/available on/sent to ISS.
These experiments were conducted in late 2020. The wipe they used was not in our payload. I have absolutely no clue how to ask them for this info.

DaveC426913 said:
Any reason you can't show us any other pics? You've got enough video to do your experiment, so you can get more pics, but maybe we'll see something in them that you've missed.
Sadly each video was about 1 minute. This is literally the only shot I have (well, a 3 second clip)

## 1. What is the purpose of identifying a length for this paper edge?

The purpose of identifying a length for this paper edge is to accurately measure the size of the paper, which can be helpful for various purposes such as printing, cutting, or fitting it into a specific space.

## 2. How do I measure the length of a paper edge?

To measure the length of a paper edge, you can use a ruler or measuring tape. Place the edge of the paper against the starting point of the ruler or tape and then measure the distance to the opposite edge.

## 3. What units of measurement should I use to identify the length of a paper edge?

The most commonly used units of measurement for paper length are inches and centimeters. However, you can also use other units such as millimeters, feet, or meters depending on your preference and the size of the paper.

## 4. Can I use a digital tool to identify the length of a paper edge?

Yes, there are various digital tools available such as online rulers or mobile apps that can accurately measure the length of a paper edge. However, it is important to ensure that the tool is calibrated correctly to get an accurate measurement.

## 5. How can I ensure the accuracy of the measured length for a paper edge?

To ensure the accuracy of the measured length for a paper edge, it is important to use a straight edge such as a ruler or measuring tape. Additionally, make sure to position the paper flat against the edge and take the measurement multiple times to get an average value.