Iron in ordinary clear float glass gives it a faint green cast that shows along exposed edges and across large panels. Low iron glass is made with far less of it, so the pane looks nearly colorless and does not tint what sits behind it. Same strength, same tempering, same cleaning. Color is the difference, and low iron costs more.
Look along the thickness at the edge of a clear panel. That green line is the iron. Through the face of a small pane you barely register it, which is why standard clear is fine on most windows and cabinet fronts. Put the same glass in a shower at 3/8 inch across a tall wide panel and the cast becomes visible against white subway tile, white grout and pale stone. It arrives as a slight cool tint laid over everything you look at through the glass.
Thickness multiplies the effect. A quarter inch pane carries less color than a half inch panel of the same glass, because light travels through more material on its way to your eye, so a tint you never noticed in a cabinet door becomes obvious in a shower. The edge is the extreme case: looking into a cut edge runs your eye along the whole length of the panel rather than across its thickness, and that far longer path through the glass is where the green concentrates.
Low iron pays off in three situations: over white or very pale tile, on tall frameless panels that cover a lot of wall, and anywhere the tile is a feature you spent real money on and want rendered honestly. Marble with warm veining, colorful mosaic and deep charcoal porcelain all shift under a green cast. Low iron shows them as they are. In a smaller bathroom with mid tone tile, standard clear looks perfectly good, and the difference in cost is better spent on thicker glass or better hardware.
There is a middle path worth knowing about. Plenty of projects use low iron on the large front panel where the eye lands and standard clear on a small return or a fixed side that sits tight against tile. Because the two are never seen edge to edge, the difference rarely registers, and the money goes where it shows. That call gets made during the measure with the panel layout in front of you.
Both are tempered to the same safety standard, cut and edged the same way in our shop and cleaned with the same routine. Neither shrugs off hard water on its own. Low iron actually shows mineral film a touch more plainly, because there is no tint for the deposits to hide behind, so the squeegee still matters just as much.
Slightly, and mostly by refusing to dim what is already there. It passes a little more light and adds no color of its own, so white tile stays white and the wall behind the shower keeps its true shade. The effect is subtle on a small pane and obvious on a tall frameless panel that covers most of one wall.
Yes, and vanities are where people notice it most. A low iron mirror returns skin tones and paint colors more accurately, which is why it gets specified for dressing areas and makeup lighting. In a standard mirror the same green cast that shows in shower glass shows up in the reflection twice over, because the light passes through the glass on the way in and again on the way out.
A color question does not survive being described in words. The Lodi selection wall keeps glass samples out where you can hold clear against low iron and lay both over a piece of your own tile. Walk in weekdays until five or Saturday until four.
