Why is it advisable to apply a coat of thin shellac after staining wood?

Applying a coat of thin shellac after staining wood is advisable because it serves to seal the stain before proceeding with further finishing steps such as applying fillers or topcoats. Shellac acts as a barrier, preventing any solvent or moisture from the subsequent applications from disturbing the stain underneath. This sealing process helps maintain the integrity and appearance of the stain, ensuring that its color and consistency are preserved throughout the finishing process.

This step is particularly important if the finishing process involves the application of other products, as it protects the underlying color achieved from the stain. Properly sealing the stained surface allows for a more uniform application of fillers or other finishes, leading to a better overall result in the final appearance of the wood.