2-pack polyurethane over shellac OK ?

[Ironwood]

I want to finish some fittings for in my shop. They are made from MDF and have been sealed with shellac.
I was going to use a 2 - pack acrylic lacquer topcoat, but my supplier no longer carries this stuff. They have 2-pack polyurethane, but I am not sure if the shellac is compatible with it.

Does anyone have any experience that they would like to pass on ?
Thanks in advance.

[Ironwood]

I may have answered my own question.
I've got some 2-pack polyurethane left over from another job. I mixed up a small batch and brushed some on the back of one of the panels.

It looks OK so far ( after 1 hour ), the paint is still a bit soft. But seems to have bonded OK.
I'll wait till its dry fully and see good it is.

[Indranil]

Just came across your 2006 post and wondered if it worked.

[rsser]

FWIW I've done one pack poly - Estapol - over a couple of sad french polished coffee tables.

One worked fine; the other developed a whitish bloom of some kind under it after some years.

[Ironwood]

Sorry Guys, I have not actually sprayed these shop fittings yet, my test pieces still look good
I have everything ready, and cleared a spot in a spare shed, once the rain stops and the humidity drops, I will get them finished.

Also copping some flack about it from SWMBO .

[Ironwood]

Well the weather came good for me at the right time. I got the bits and pieces sprayed over 2 days.
The results look great. No trouble with the 2pack poly bonding to the shellac it seems.

Not sure if photos would help, but I will take a couple and see what they look like.

Charcoal coloured MDF shop fittings are nothing to get too excited about.

[Ironwood]

Heres one thats going to the shop tomorrow.

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