Plaster Repair

I've seen few threads on repairing plaster surfaces and have seen some plaster repair materials/kits in the stores but, have never seen any explanation as to why you can't or shouldn't repair plaster with drywall mud.

Any input/thoughts on doing this ?

You will be lucky if you don't fifteen deffernt answers
http://www.askthebuilder.com/repairing-plaster-walls/

Drywall mud has a different density thus response to changes in temperature and humidity. This can lead to cracks because the different materials expand and contract at different rates.

I have used drywall mud to repair plaster for 30 years and have never had a bad result. I started out years ago using paper tape as that was all I could find but have switched totally to the mesh tape. Large holes I patch over lath with drywall and just tape and fill the cracks. Plaster that is loose I use the large plaster washers to pull it back tight and then tape and mud. It’s tempting on hair line cracks to skip the tape but the crack will always come back if I don’t tape it 100%. A wider crack I will fill first with mud and trowel it flush with the plaster and then after it dries and shrinks then tape it. 2 inch tape is all you see around so sometimes I use two strips overlapped.

Setting plaster there is nothing wrong with and if you have a lot to fill it works great as it doesn’t shrink. But for normal repairs around boxes when I do wiring and stuff the drywall mud works great and really locks the box in tight.

I make up ½ plywood plates with the cutout for a box many times when working with old lath plaster and screw them to each piece of lath where I made the hole and then skim coat and fill the cracks with tape and drywall mud right up to the box. When done it looks like it’s been there for 100 years.