THE WATER TESTPart 1 · Step 1 of 7
Step 1Test the water1 min

Collect 100 mL of water

Filling the amber glass jar with water at the faucet

Fill the jar almost to the top with the water you're testing. It holds about 100 mL (3.5 oz). Leave room for the 1 mL vial you add next. Results are reported per 100 mL, so use the full jar.

Step 2Test the water15–20 min wait

Add the vial and wait

Adding the reagent vial to the amber glass jar with a dropper

Add the vial, swirl gently, and wait 15–20 minutes. Longer is better; the dye needs time to bind.

Cover the jar while you wait. Dust from the air lands in an open jar and gets counted.

Step 3Test the water1 min

Put the filter in the holder

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

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

Step 4Test the water1 min

Attach the holder to the syringe

Choose the syringe connector that matches yours, then watch the short video before attaching the membrane filter holder.

Which connector does your syringe have?

Step 5Test the water1 min

Fill the syringe

Pouring prepared water into the top of the syringe

Pour the prepared water into the top of the syringe.

How many times to fill it

If you have a 60 mL syringe, fill and push it roughly twice. If you have a 100 mL syringe, fill and push it once. Either way, keep going until the jar is empty so the full 100 mL sample passes through the same filter.

Unscrew the filter holder before you pull the plunger back for the second fill. Pulling against the filter can damage it.

Step 6Test the waterRight away

Push the water through

Pushing a water sample through the syringe filter

Push the water through right away; don't let it sit.

Step 7Test the water1 min

Retrieve the filter

Unscrewing the filter holder to retrieve the filter membrane

Unscrew the holder and take out the filter. Keep the side that faced the water pointing up. That's the side you read.

Step 1Find the particles

Use the microscope

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

Two things to check

These details can make particles harder to see. If the screen looks unusual, check both before reading the result.

Keep the membrane very flat

If the 25 mm filter disc curls or buckles, the light can hit it unevenly and create darker areas. Handle it with the tweezers and try to keep it very flat while you read it.

Dab it with a paper towel until slightly damp. Damp makes the disc stick flat; bone-dry, it curls.

Check the flashlight batteries

The flashlight is fixed in place, 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. You won't see it happen: a half-dead cell still throws a beam that looks bright. If the kit was finding particles and then stopped, put in fresh batteries before you trust a clean result.

Watch a full test with the previous kit

This video uses the previous version of the kit, but the water-testing process is the same: add the dye, check the blank filter, push the water through, and count what glows. Watch the blank check at 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 suspected microplastic can look like

Suspected microplastics can appear as small glowing dots, fibers, or dark marks. Use these views as a reference while reading the filter.

Count theseSuspected particles

The color varies with the lens and the light: deep red, warm orange, or almost blue. Every view below counts.

What you're looking at

  • StringsPotential polyester fibers.
  • Black marksBlack plastic, carbon, or other dark debris.
  • Glowing dotsThe suspected microplastic.

A long fiber may be polyester, or it may be cotton or rayon, which aren't plastics, or a clothing fiber that landed from the air while your sample sat open.

Carbon shed by a carbon filter, grit, rust and other debris all look like black specks at 10x, the same as black plastic. Looking at one doesn't tell you which it is. More on this.

Microscope view with microplastic particles — faint glowing dots on a deep red background
Two suspected microplastics near the top left.
Microscope view with a cluster of faint glowing dots on a deep red background
A count of six indicated microplastics.
Microscope view with a single bright dot low on a deep red background
A count of four indicated microplastics.
Microscope view with microplastic particles on a warmer, orange background
A count of seven indicated microplastics. A slightly orange tint is normal.
A second microscope view with particles on a warmer, orange background
A count of four indicated microplastics. An orange tint is normal.
Blue microscope view showing specks and short fibers on the filter membrane
Over 15 indicated microplastics here. Notice the 3D texture (shadows).
Blue microscope view showing seven marks on the filter membrane
A blue background is also okay. 4 of the 7 particles here have 3D texture. Notice the shadows.
A microplastic fiber glowing on the filter membrane, with a dark speck beside it, at 10x
Potentially one polyester fiber, and one black particle — black plastic, carbon, or other dark debris.
A short bright fiber near the top of the filter membrane
This looks like another potential polyester fiber and an indicated microplastic.
A long curved fiber running across the filter membrane
A long fiber in a tap water sample.
A thin fiber with bright points along it on the filter membrane
One long fiber and one indicated microplastic particle.
A couple of faint bright points low on the filter membrane
A count of five indicated microplastics and one small indicated plastic fiber.
Several small bright dots scattered across the filter membrane
This appears to be a count of four indicated microplastics.
A dark elongated particle in the middle of the filter membrane
Notice the indicated fiber and one black particle (potentially carbon or PEX/plastic).
Not theseNo microplastics

These images do not show any microplastics. An even view with no distinct glowing dots — nothing to count.

An even blue view with no particles on the filter membrane
An even background with no distinct marks.
Microscope view with no particles on the membrane (example 2)
No microplastics indicated. Ignore small blotches.
Microscope view with no particles on the membrane (example 3)
No microplastics indicated. Ignore small blotches.
Microscope view with no particles on the membrane (example 4)
No microplastics indicated. Ignore small blotches.
Microscope view with no particles on the membrane (example 6)
No microplastics indicated. Ignore small blotches.

Want to test again?

Each refill covers one more run — keep the microscope, syringe, and filter holder you already have. sold separately.

Get a refill

Stuck on a step? Use the chat in the bottom-right corner.

Don't have a kit yet? The microplastics test kit is available to order online. Tests are sold separately.

Using the previous digital-microscope rig? Open the legacy instructions.