Why not use hardware store finish?

[HooligansMusicLab]

Hi everybody,

There's a really clear consensus that we shouldn't use the products you can find at your local hardware store for guitar finishing (like minwax stain, or polyurethane), but I haven't seen any explanation why. What are the problems and pitfalls that come with those products? What makes them unsuitable for guitars?

Thanks!

[dingobass]

Good question.

Most of your hardware store finishes are designed for furniture, but having said that, poly and mini wax (shudder) can be used with success.
Most of your Music Shop cookie cutters are finished with Poly.

Things to avoid are automotive finishes as these are designed for coating metal, which doesnt breath and move like timber.
Acrylic takes forever to cure on timber, you can leave it for a month and lay it on your bench and find that whatever you use as a bench top protector (towel, gym mat etc) will leave marks indented into the finish.
It may appear to be cured but quite often if you gently press your thumb nail onto the surface you will find it leaves a dent quite easily.
This is due to layers under the top not being fully cured. This leads to other problems such as shrinkage, cracking, sink into the grain and go milky.
These are just a few reasons why acrylics are not widley used In Luthiery.

Hope that answers the question.

[HooligansMusicLab]

Yes, thanks for the info!