High-density (HD) printing gets its height from the stencil, not from foaming. The printer builds a thick stencil with heavy emulsion or a capillary film, then prints a dense ink through it, sometimes in more than one stroke or layer. The result stands up from the shirt with crisp, flat-topped edges that look molded rather than puffed.
HD keeps more definition than puff, so it works for raised logos, geometric shapes, textured lettering and stacked effects. A clear HD layer over a color can give a glossy, gel-like finish. It takes longer to set up and print than standard ink, uses more of it, and the raised area is firmer and heavier, which matters on lightweight tees.
Ask how tall the print will be, whether it is flashed between layers, and how it feels after washing. Compare it with puff ink in the puff and high-density guide.