When glass processors shop for a washing machine, the first thing most of them look at is washing speed.
But with Low-E glass, speed isn't the number-one spec. What really counts is whether the machine can meet high-cleanliness washing requirements.
On a machine built for Low-E glass, the brushes, air knives, water circulation and filtration system, and water quality all directly affect the washing result and the surface quality of the glass. Low-E coatings are fragile — the water treatment or brush material on a standard machine can damage the coating and cause it to fail. And if the air knife section is poorly designed, drying performance suffers too. So judging whether a machine is right for Low-E glass means looking at all of these factors, not just speed.
Let's start with the brushes.
Brushes come in two types: black stiff brushes and white soft brushes. For machines that wash Low-E glass, factories go with the white soft ones — but soft brushes vary from factory to factory.
At international glass trade shows, I've come across component suppliers whose brushes have bristles that are too stiff and planted too sparsely. After those shows I visited other factories and saw the same problem. Brushes like that are good enough for regular float glass at best — they can't handle Low-E glass, which demands far higher cleanliness.
So as a buyer, what does a proper Low-E soft brush actually look like?
First, check how soft the bristles are. Bristles that are too stiff won't just clean poorly at high washing speeds — they can damage the coating on Low-E glass (leaving brush marks on the surface) and even snap off. Think of the brush as a broom in your house: stiff broom bristles struggle to pick up dust off the floor, soft ones don't. A qualified soft brush should feel fluffy and pleasant to the touch. That's the kind of brush that won't hurt your glass.
Next, look at how the bristles are arranged. On the market, bristle patterns fall into two types: straight and spiral.
Take the straight pattern first — the bristles run straight along the roller. As the brush rotates, a whole row of bristles hits the glass surface at almost the same moment. Wash water flows into the gaps between the bristles, carrying dirt in with it. With this straight up-and-down scrubbing motion, there's no sideways force to push contaminants out, so dust and glass dust keep swirling around in the gaps. It can't meet the cleanliness standard for Low-E glass.
Now the spiral pattern — the bristles run diagonally along the roller. Instead of a full row contacting the glass all at once, the brush touches the glass progressively, sweeping along a fixed angle. Water and dirt are pushed outward along that angle, so dust and glass particles are far less likely to get trapped between the bristles.
That's why straight-pattern brushes struggle with high-cleanliness Low-E glass, while spiral brushes clean more efficiently. I'll add photos of both patterns below so you can see the difference.
By the way, this brush design is a SUNBO patent.
The last factor is bristle density. Too few bristles and the dust won't come off the glass — you need enough of them to wash properly. There are two ways to judge this. First, before washing: look at how full the brush appears. On a black stiff brush, you can clearly see the base of the bristles from the front, though not when you look from behind at an angle. On a white soft brush — fluffy and soft by nature — you shouldn't be able to see the base easily from the front. Second, after washing: a brush with plenty of bristles holds more water in the fill. Pinch the bristles between your fingers — if they feel noticeably wet, the density is good enough.
When you're choosing a Low-E glass washing machine, the brushes aren't a throwaway detail. Bristle softness, arrangement and density — all three affect how clean your Low-E glass gets.
