Tuesday, August 2, 2011

Grand Piano Restoration: Lacquer Curing

After the tuning pin holes have been re-sized the restoration project in this area will be dormant for about two weeks.

When lacquer is sprayed it must be given time to “cure” properly. The reasons for this are two-fold but both reasons are connected to one another: 

Spraying furniture finish through a spray gun requires the mixture to have the consistency of water. This means that the mixture has a high concentration of solvent to allow the proper flow through the spray equipment. After spraying, the product must be allowed to “gas-off” which means that the solvent evaporates out of the finished product.

While the gas-off process is on-going, the lacquer applied to the surface shrinks because of the solvent loss; at the same time, the catalyst in the lacquer hardens and stiffens the lacquer to its characteristic hard shell, or tortoise shell. The following day after spraying, the lacquer feels hard to the touch, this is only the outside surface to a certain extent; the lacquer underneath is still swimming. 
Because of this I am unable to tape off sections of the plate in order to re-string.  The lacquer is not fully cured; when attempting to remove the tape after stringing, often times this will rip off the plate gilding, causing problems.

Waiting for this process to complete allows us to move over and continue on with another area of the project; we will begin the refinishing process of the cabinet this week.

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