Here is an example of what size failure looks like. This #140 Stonehenge HP was sized with gelatine size, hardened with glycol and applied in two layers by brush. Size is necessary to cause the pigmented emulsion to sit on the surface of the paper, not soak into the fibers of the paper where the pigment particles get trapped causing staining. During the multiple washes to clear the dichromate and remove the unhardened gum, the thin areas wash away and leave the raw paper open for the pigment to soak in and stain. To avoid this, one can either do more layers of size before printing or add additional layers of size between the layers of emulsion as one prints.