[Evolution] Fixing the font size in composer?

["Alasdair McAndrew" <amca01 gmail com>]

Now, I can change the size of the font in a variety of ways, such as choosing HTML as message format, and then increasing the font size.  But the annoying thing is that the moment I press my return key (such as to start a new paragraph) the font returns to its original tiny size.  This is 
most  annoying.  How do I set the font size once and for all so that it will stay fixed for the entire duration of my message?  (And if possible, for all other messages thereafter.)

Thanks,
Alasdair