A finished altarpiece was not automatically paid for. Most contracts built in a moment of judgment: the patron, or a named deputy, had to declare the work acceptable before the final instalment was released. That clause was not mere formality. It was the mechanism by which the price negotiated at the start could be quietly renegotiated at the end — upward if the work exceeded expectations, downward if it fell short.
The typical arrangement named two stimatori — assessors, one appointed by each party — whose job was to value the completed work independently and then agree a figure. If their estimates converged, the final payment followed. If they diverged, the contract usually specified a third party, a terzo arbitro, whose judgment broke the deadlock. This person was almost always a practising painter, often a local one of standing, occasionally a goldsmith or architect if the dispute turned on materials rather than execution. The choice mattered: a craftsman from the same city understood local rates and could inspect the pigments without being deceived.
Disputes tended to cluster around a handful of issues. The quality of blue was the commonest flashpoint — whether the painter had used the ultramarine specified in the contract or had substituted the cheaper azurite. Gold leaf was another: its weight and coverage were quantifiable, and a careful assessor could check both. Beyond materials, arguments arose over the mano del maestro — the master's own hand — when a patron suspected that assistants had painted more than the contract permitted.
The arbitration record that survives in notarial archives shows these processes were used and not merely threatened. Painters sometimes came out ahead: an assessor might find the work worth more than the contract price and the patron was bound to pay the difference. The clause cut both ways. What the system achieved, across hundreds of individual commissions, was a settled expectation that quality had a measurable standard — not an aesthetic one exactly, but a contractual one, legible to anyone who knew what lapis lazuli cost by the ounce and what a day's work in fresco was worth.
