THE WATER TESTPart 1 · Step 1 of 2
Step 1Set up the rig1 min

Slide the flashlight into the rig

Down the channel until it seats

Slide the flashlight down the angled channel, head first, until it seats against the round housing. The channel sets the angle, so there's nothing to aim.

Low batteries make a real sample read as clean, and the beam still looks fine when they're low. If it worked before and then stopped, swap them.

Step 2Set up the rig1 min

Put the microscope in the rig

The digital microscope seated in the rig's round housing, screen facing up

Unwrap the digital microscope and press the power button. Drop it into the round housing, screen up, so the lens looks down at the light. Leave the wand aside until you have a filter to read.

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

Twist the holder onto the syringe tip until snug

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

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 1Assemble the microscope and find the particles1 min

Put the filter on the wand

Laying the round filter membrane flat on the wand with tweezers

With the tweezers, lay the filter flat on the wand, collection side up. Slide the wand into the rig until the filter sits under the microscope and over the light. A curled disc throws shadows that read as empty filter, so get it flat.

Dab the filter with a paper towel until slightly damp. Damp lies flat; bone-dry curls.

Step 2Assemble the microscope and find the particles2–5 min

Move the wand to search the filter

Move the wand around under the microscope to hunt for microplastic particles

Switch on the microscope. The lens sees a small patch at a time and the particles are scattered, so move the wand in and out and side to side until you have covered the whole disc. Go slow and overlap your passes.

Step 3Assemble the microscope and find the particles2 min

Count the glowing dots

The microscope screen showing faint glowing dots on a red background

Each faint glowing dot or short fiber is a suspected microplastic. Count them as you go. The color varies with the lens and the light — more red or less red is fine. Compare against the examples below.

  • 0–2No microplastics indicated
  • 3–6Microplastics detected
  • 7+Relatively high quantity of microplastics

Your count is a floor. The membrane is 1 µm, so anything smaller passes straight through, and some of what lands is too small to resolve. For every particle you can see, there are more you can't.

Swipe or tap the arrows to continue

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.

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. Each arrow points at one thing to count.

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

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Have the current kit? Open the current instructions.