# Finish Compatibility Matrix

Rules for layering finishes. "Over" means applied on top of a cured layer.

## The Golden Rule
**"Fat over Lean"**: More flexible finishes can go over harder finishes, but rarely vice-versa.
**"Polar over Non-Polar"**: Generally risky.

## Matrix

| Base Layer | Top Coat: Nitro | Top Coat: Poly | Top Coat: Shellac | Top Coat: Oil | Top Coat: Waterborne |
| :--- | :--- | :--- | :--- | :--- | :--- |
| **Raw Wood** | YES | YES | YES | YES | YES |
| **Shellac** | YES (The universal sealer) | YES (Dewaxed only) | YES | NO (Oil won't penetrate) | YES (Dewaxed only) |
| **Nitrocellulose** | YES (Melts in - burn in) | NO (Adhesion failure) | YES | NO | NO |
| **Polyurethane** | NO (Crazing risk) | YES (Scuff sand) | YES | NO | YES (Scuff sand) |
| **Oil (Cured)** | NO (Unless fully cured 30+ days + Shellac barrier) | NO | YES | YES | NO |
| **CA Glue** | YES | YES | YES | NO | YES |
| **Vinyl Sealer** | YES | YES | YES | NO | YES |

## Special Notes
- **Oily Woods (Cocobolo, Rosewood):** Must be sealed with **Shellac** or **Vinyl Sealer** before applying Nitro or Poly, or the finish will not cure.
- **Waterborne:** Extremely sensitive to stearates in sandpaper and wax in shellac. Always use dewaxed shellac.
