Sealing watercolour painting

I didn’t know about this but thought you might be interested.  

I like to send artful snail mail and most of the time I have mail it out in an envelope because it is watercolour and I’m afraid it might become damaged in transit.  This would work too if you wanted to frame and hang an artwork without the cost (and trouble) of getting glass cut. I saw this somewhere on Utube: they used Gamblin cold wax medium.  I don’t have that so I used what I did have........Dorland’s wax medium.  Yes it does work, this little trial piece is sealed.  I used pen with watercolour over the top for this test piece.  I had used some copper metallic paint too and as expected it became matte under the wax.  I know it is obvious but I needed to try.  I cleaned off the water and watercolour paint without harm to the painting below.