Restoring 'Piano Black' (Polyester Resin) Grand Piano Top - Sanding and Polishing

Timelapse video showing a 5 hour sequence shortened to 5mins! Sanding and polishing a 6' (1.86m) grand piano top. The original 35 years old polyester resin was dull, scratched and revealed surface imperfections including expansion/contraction of the wood beneath (grain ripples). Older resin gloss is particularly hard and 'cured' making the sanding and polishing process challenging compared to a newly-applied gloss. Long-cured polyester resin is especially stubborn, making it a very hard-wearing finish for premium musical instruments and furniture. The black pigment is within the gloss finish itself, rather than a colour mid coat with a clear top coat. In original manufacture, the polyester resin finish is usually applied to ~3mm thick and sanded back to 0.8mm for final finish in manufacture. In the life of the instrument, polyester resin at almost 1mm thick allows for 2 or 3 refinishing stages restoring a perfect 'new' finish from the original manufactured finish. Dry sanding stages are p320 to remove significant scratches, then p500, p800, p1500, coarse compound with twisted wool mop, medium cut compound with lambswool mop. The final stage finishing compound and polish with light foam sponge.