Making lithographic printing plates

A method for forming a lithographic printing plate, comprising:

• imagewise exposing a positive-working lithographic printing plate precursor with infrared radiation to form an imaged precursor comprising exposed regions and non-exposed regions in a first ink receptive layer and a second ink receptive layer, if present, and
• processing the imaged precursor to remove the exposed regions of the first ink receptive layer and of the second ink receptive layer, if present, using a silicate-free processing solution having a pH of at least 12 and up to and including 14 and comprising at least 0.001 gram-atom/kg of a metal cation M2+ selected from the group consisting of barium, calcium, strontium, and zinc cations;
• the positive-working lithographic printing plate precursor comprising
• a grained and anodized aluminum-containing substrate,
• a poly(vinyl phosphonic acid) interlayer disposed directly on the grained and anodized aluminum-containing substrate,
• a first ink receptive layer that is disposed directly on the poly(vinyl phosphonic acid) interlayer, the first ink receptive layer comprising at least one water-insoluble, alkali solution-soluble or -dispersible resin, and an aromatic acid dye that is Naphthol blue black, Trypanblau, Direct Blue 71, or Diamingrün having the structures shown below,
• the aromatic acid dye being present in an amount of at least 0.5 weight %, based on the total dry weight of the first ink receptive layer,
• the positive-working lithographic printing plate precursor being infrared radiation-sensitive and further comprising an infrared radiation absorber in either the first ink receptive layer or in an optional second ink receptive layer that is disposed over the first ink receptive layer, or in both of the first and the second ink receptive layers,
• Direct Blue 71
• Naphthol blue black
• Diamingrün
• Trypanblau