An IP rating like IP67 is two separate test results: the first digit grades protection against solids (dust), the second against water. IP67 means dust-tight and able to survive shallow immersion; IPX4 means splash-resistant, with the X indicating the product was never tested for solids at all. Founders often request "make it IP67" the way they'd request a color, assuming it simply means "waterproof." In reality an IP rating is a very precise and very narrow statement: a brand-new unit passed a defined test, under defined conditions, against one specific kind of ingress — and nothing more. Understanding that gap is the difference between a spec that protects you and a promise that comes back as returns and warranty claims.
Two Digits, Two Completely Different Tests
- First digit — solids. Runs 0 to 6, describing protection against intruding objects: a finger, a tool, a thin wire, and finally dust. A 5 means dust may enter but not enough to impair function; 6 means fully dust-tight.
- Second digit — water. Runs 0 to 9, and each value is a different scenario: vertical drips, angled drips, spray, splashing, jets, powerful jets, temporary immersion, deeper continuous immersion, and high-pressure high-temperature washdown.
- X in place of a digit. IPX7 means tested for water only, with no solids test at all. It's a statement about a missing test — not about complete protection.
Why the Water Scale Is Not Cumulative
Intuition says a higher number includes all the lower ones. That holds up through jets, then breaks down. A product that survives immersion does not necessarily survive a pressurized jet: immersion tests uniform hydrostatic pressure, while a jet tests concentrated mechanical force driving water through seams. A product that must survive both has to be tested for both, and the spec should say so explicitly — for example "IP65/IP67." This trips up washdown products constantly: kitchen equipment, agricultural gear, clinical devices that get hosed or scrubbed.
The Test Conditions Define the Meaning
IP tests are defined by an international standard (IEC 60529) and are exacting: liters per minute, distance, angle, duration, immersion depth, unit orientation. Three details worth knowing:
- Fresh water at room temperature. Not seawater, not pool water, not soapy water. Salt and detergents lower surface tension and creep through seams that clean water never passes.
- A new unit, not a used one. Testing is done on a fresh sample. A gasket compressed through thousands of open-close cycles, scratched, or aged in sunlight is not the same gasket.
- No temperature shock. A warm product dropped into cold water develops negative internal pressure and sucks water in — a real field scenario the standard test does not simulate.
What the Rating Does Not Promise
Four promises the rating never makes: it doesn't cover chemicals, solvents, or cleaning agents; it doesn't cover steam or sustained humidity condensing inside; it doesn't guarantee the same performance years into the product's life; and it doesn't cover what happens after the user opens a cover. A well-engineered product therefore never relies on the rating alone — it assumes some moisture will get in and designs for it: drainage paths, conformal coating on the PCB, and careful placement of sensitive components. Sealing strategy is a materials-and-mechanics problem — gasket selection, groove design, and enclosure plastics all interact, which is why it belongs inside your design-for-manufacturing thinking and your choice of enclosure plastic from the start.
How You Get a Rating You Can Print on the Box
A claimable IP rating comes from an accredited laboratory testing several representative production units — not a 3D-printed prototype. You specify the target rating, the lab runs the standard test and issues a report, and that report is what lets you state the rating to customers and retailers. Plan for it in the validation builds of your EVT/DVT/PVT sequence, because a sealing fix discovered after tooling is one of the most expensive changes in hardware. And note that an IP test doesn't replace safety certifications like UL or FCC — it's in addition to them, as covered in product safety testing requirements. Budget both the lab test and at least one design iteration on the seals before moving from prototype to production. More guides live in our new product development hub.
Designing a product that has to survive rain, washdowns, or a swimming pool? Contact Projects House and we'll engineer the sealing strategy — enclosure, gaskets, and test plan — to match the rating your market actually needs.