THE WATER TESTWatch first
Watch first3 min

Watch: the digital microscope kit

Your kit includes a digital microscope. Watch this quick walkthrough first, then follow the steps below — the sample prep is the same, only the imaging changes.

Filling the amber glass jar with water at the faucet
Step 11 min

Collect 100 mL of water

Fill the jar we provided almost to the top with the water you're testing — it holds about 100 mL (3.5 oz). Leave a little room for the 1 mL vial of reagent solution you'll add next. Volume matters: your result is reported per 100 mL.

Adding the reagent vial to the amber glass jar with a dropper
Step 215–20 min wait

Add the vial and wait

Add the vial, swirl gently, and wait 15–20 minutes. Two vials? Add the first, swirl, wait 15 min — then the second, swirl, wait 15 more.

Cover the jar while you wait — dust from the air can land in an open jar and get counted.

Step 31 min

Put the filter in the holder

Unscrew the holder, set the round filter membrane inside, and screw it back together.

Open the holder, drop the filter in, twist it shut

Step 41 min

Attach the holder to the syringe

Twist the assembled filter holder onto the syringe tip until it's snug.

Twist the holder onto the syringe tip until snug

Pouring prepared water into the top of the syringe
Step 51 min

Fill the syringe

Pour the prepared water into the top of the syringe. It holds 60 mL, so you'll fill and push it about twice.

Pushing a water sample through the syringe filter
Step 6Right away

Push the water through

Push the water through right away — don't let it sit. Everything we count is caught on the filter surface.

Unscrewing the filter holder to retrieve the filter membrane
Step 71 min

Retrieve the filter

Unscrew the holder and take out the filter. Keep the side that faced the water pointing up — that's the side we image.

The microscope screen showing microplastic particles as faint glowing dots on a red field
Step 82 min

Look at the filter under the microscope

Set the filter on the microscope stage, collection side up, and switch on the light. Slide your phone into the stand so its camera looks straight through the lens, then move it around and focus until the field is sharp. On the red screen, each faint glowing dot is a piece of plastic — that's your result, right there under the lens. Compare against the examples below.

Swipe or tap the arrows to continue
Have the original photo-box kit? See those steps

Two things that stop it from working

Both of these make a sample with plastic in it look clean. If your screen suddenly shows nothing, check these before you trust the result.

The #1 issue

Keep the membrane dead flat

By far the most common reason a real sample reads as clean: the 25 mm filter disc is curled. If it curls or buckles, the light hits it unevenly and you get dark patches that look like nothing's there — that's shadow, not a clean filter. Handle it with the tweezers — that's what they're really for, keeping it flat matters more than contamination — and get it lying completely flat before you image.

Trick: dab it with a paper towel to a slightly damp state. A little moisture makes the disc stick flat to the surface; bone-dry, it tends to curl.

Check the flashlight batteries

The flashlight sits in a fixed position, so aiming isn't the problem — the batteries are. Below about 50–70% charge, the blue light stops exciting the dye and nothing glows, even with plastic on the filter. If particles were showing a moment ago and then vanished, swap or recharge the batteries before you assume the sample is clean.

Watch a full test, end to end

A real 100 mL sample of bottled water, start to finish: add the dye, check the blank filter, push the water through, and count what glows. Note the blank check around 0:40 — look at the filter before any water runs through it, count anything already glowing, and subtract that from your final number.

Compare two sources

Have two tests? Run one on unfiltered tap water and one after your filter.

When you're done

Wash the jar thoroughly. Don't drink from it.

What a plastic particle looks like

You read the result yourself under the lens. On the red screen, each microplastic particle shows up as a small, faint glowing dot — often subtle, sometimes easy to miss. A clean sample is an even red field with no distinct dots. Use these as a reference, then count the dots you see.

Count theseParticles present
Microscope view with microplastic particles — faint glowing dots on the red field (example 1)Microscope view with microplastic particles — faint glowing dots on the red field (example 2)Microscope view with microplastic particles — faint glowing dots on the red field (example 3)Microscope view with microplastic particles — faint glowing dots on the red field (example 4)Microscope view with microplastic particles — faint glowing dots on the red field (example 5)Microscope view with microplastic particles — faint glowing dots on the red field (example 6)
Not theseClean field — no particles
Clean microscope view — an even red field with no particles (example 1)Clean microscope view — an even red field with no particles (example 2)Clean microscope view — an even red field with no particles (example 3)Clean microscope view — an even red field with no particles (example 4)Clean microscope view — an even red field with no particles (example 5)Clean microscope view — an even red field with no particles (example 6)

Want to test again?

The Refill 4-pack covers 4 more runs — keep the microscope, syringe, and filter holder you already have. $28.

Refill 4-pack — $28

Stuck on a step? Use the chat in the bottom-right corner — we reply fast.

Don't have a kit yet? The microplastics test kit is $75. Tests are sold separately.