The short version
- Inspect after washing, not before — crazing shows best on a clean wet surface.
- Hold the light at a shallow angle to the wall, not straight at it.
- Crazing plus a failed leak test ends regulated service permanently.
- A crazed bottle in a sound cage is exactly what rebottling exists for.
What is actually happening in the material
HDPE is a semi-crystalline polymer. Under repeated stress the amorphous regions between crystallites begin to pull apart into fine voids bridged by drawn-out polymer fibrils. Those voids scatter light, which is why they appear white against otherwise translucent plastic.
That is the textbook version. The practical version is that every fill and every draw-down works the wall slightly, and the material has a finite number of those cycles in it. Six to eight full service cycles is our yard average before the bottle is genuinely at end of life, though it varies enormously with what was in it and where it was stored.
Three things accelerate it: dense liquids, which increase the stress per cycle; ultraviolet exposure, which embrittles the surface and gives cracks somewhere to start; and certain chemicals, which cause environmental stress cracking at loads the material would otherwise shrug off.
Where it appears, in order
| Location | Frequency | Why there | Severity |
|---|---|---|---|
| Lower corners, outlet side | Most common | Highest hydrostatic load plus outlet stress | Serious — this is where leaks start |
| Lower corners, opposite side | Common | Hydrostatic load | Serious |
| Shoulders, upper corners | Common | Flex during handling and stacking | Moderate |
| Around the outlet flange | Occasional | Over-torquing, not fatigue | Serious — often terminal |
| Mid-wall, flat panel | Uncommon | Usually vacuum damage or impact | Depends on cause |
| Around the collar | Uncommon | Clamping stress from a poor rebottle | Serious |
The pattern tells you something. Crazing at the lower corners is normal ageing. Crazing around the outlet flange is usually somebody with a wrench. Crazing around the collar on a rebottled unit means the bottle was pushed rather than pressed into the cage — which is why we press.
How to actually see it
Three things make the difference between finding crazing and missing it entirely.
Inspect after washing
A clean, wet surface shows crazing far better than a dusty dry one. Water fills the surface texture and the white network stands out against it. We built our grading sequence around this — units are re-inspected after the wash, not only before it.
Rake the light across the wall
A torch held perpendicular to the surface washes everything out. Held at a shallow angle, ten or fifteen degrees, the crazing lights up. This is the single technique that separates people who find it from people who do not.
Look from inside where you can
A borescope through the lid shows the inner surface, where crazing frequently starts before it is visible outside. We use one on anything destined for regulated service or food-grade resale.
How much life is left
This is the judgement call, and I will give you the rubric we use rather than pretend it is a measurement.
| What you see | Our decision | Rough remaining life |
|---|---|---|
| Nothing under raking light | Grade normally | Full remaining life |
| Faint patch smaller than a hand, passes leak test | Sell, flag for re-inspection at next wash | 2–4 cycles |
| Visible from three feet in ordinary light | Grade B at most, no food-grade, no regulated | 1–2 cycles |
| Running along a corner seam | Rebottle or scrap | 0 — do not fill |
| Any crazing plus a failed leak test | Granulate the bottle | 0 |
| Crazing around the outlet flange | Usually scrap; flange is distorted | 0 |
The one I will not compromise on
Which is exactly why rebottling exists
Here is the thing that makes crazing bearable commercially. The bottle wears out. The cage does not — galvanised steel tube in a covered yard will outlast three or four bottles comfortably.
So a container arriving with a badly crazed bottle in a straight, sound cage is not a scrap unit. It is a rebottling candidate: strip the old bottle, granulate it, straighten and inspect the frame, press in a new virgin bottle, and you have avoided 78 lb of virgin steel while giving the customer a factory-clean interior.
That is about a third of what leaves our gate now. Every one of those started as somebody looking at a white network in a corner and deciding the container was finished. It was not — half of it was.
Written by Desmond Okafor, yard manager at IBC Totes San Francisco. Published October 16, 2025. Spotted something wrong? Tell us — we would rather fix it than defend it.