Finishing schedule versus curing time
A workshop is finishing eight spotted gum display plinths with a two-pack polyurethane clear coat. The product data sheet specifies a 16-hour minimum recoat interval at 25°C, and a maximum interval of 48 hours before sanding is required. The workshop is at 18°C and the job must be packed and transported in three days. The finisher plans to apply three coats: sealer, then two topcoats, sanding between coats. The plinths are being finished in an open bay next to a door that is opened frequently for deliveries, and a dusty extraction duct passes overhead. The client wants a high-gloss finish with no visible dust nibs.
1. Assess whether the three-day schedule is realistic and identify the finishing risks.
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The schedule is tight and probably unrealistic as planned. At 18°C the recoat time will be longer than the 16-hour figure quoted at 25°C, because two-pack polyurethane cure is temperature-dependent; the finisher should expect perhaps 20–24 hours between coats. Three coats with two recoat intervals therefore consume roughly two days before any sanding or final cure, and the product will still be soft when packed. The dust risk is significant: a frequently opened door and an overhead extraction duct in an open bay will deposit dust on a high-gloss wet film, and high gloss shows every nib. The maximum 48-hour recoat window also matters - if the job stalls over a weekend, the surface may need sanding before the next coat, adding time.
2. What should the finisher do to protect quality while meeting the deadline?
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Separate the plinths from the dust source: move finishing to a dedicated area or screen the bay, seal or re-route the extraction duct, and restrict door traffic during flashing-off and cure. Control temperature - heat the bay to at least 25°C to bring recoat times closer to the data sheet and shorten the overall schedule. Sequence the work so all eight plinths receive the same coat on the same day, which keeps them within the recoat window together and avoids one piece falling outside the 48-hour maximum. Build in a final cure period before packing, because packing a soft two-pack film causes blocking and imprint marks. If the deadline cannot accommodate a proper cure, the finisher should tell the client rather than deliver a finish that will mark in transit.