Black and Blue Magic...

I can't believe I finally found out the title to this book. I have been searching for this book for probably over 20 years.
I had read "Black and Blue Magic" by Zilpha Keatley Snyder back in the early 70's, I think. It was about a clumsy boy who was supposedly descended from Houdini, who was staying at a boarding house for the summer, was really bored, and working there made his shoulders sore. (I forget what he did) He got this ointment from an older gentleman. When he rubbed it on his sore shoulders at night, he grew wings! He had such adventures!
I remember being so entranced by the idea that this boy could fly and how he could escape his humdrum life each night. At the time, (I think I was 8 or 10?) flying was something I was fascinated with, and used to dream that I could. (Funny how I can remember that dream to this day, even though this was back in the 70's!!)
This book came to mind many times over the years, but I could never remember the name of it til I found it on a website today. I found it on 'Loganberrybooks.com'. It seems to be a search site where you can put in information about a book you once read, but could no longer rememer the title. I can't believe how many people had read this same book and made inquiries.
Well, I'm delighted to finally solve that mystery. I would like to read this book again to see if it was as good as I remember, so maybe I will check my local library, or perhaps EBAY.