Primer, printing set, printing method, and printing apparatus

A system comprising a primer and a recording material,

• wherein the primer comprises:
• water;
• a cationic resin;
• a polyvalent metal salt;
• a diethylene glycol alkyl ether-based organic solvent, and
• 3-methoxy-3-methyl-1-butanol,
• wherein a content of the polyvalent metal salt in the primer is 0.25% by mass or more and 10% by mass or less, and
• wherein a content of the cationic resin in the primer is 2% by mass or more and 15% by mass or less, and
• wherein the recording material comprises a non-permeable recording material.