After applying the sealing coat of polyeurethane, I realised the stain had been turned to liquid by the thinner with clear marks resulting... I'd put the job off for long enough. Bought a cheap belt sander and got to work, finishing with a vibration sander attached to our trusy hard-working Dyson vacuum cleaner.
Thankfully applying the stain afterwards showed no marks from before. This was obviously the first coat. 2nd coat made it all look a lot more uniform.
This time I took the precaution of using the backsides of a couple of plank's scraps to apply stain and test. It ran again, so it hadn't been the fact that I'd oiled the wood to get a more uniform coating before. The stain clearly isn't compatible with the Polyeurethane varnish. Spoke with Arnie and he has a couple of cans of sanding sealer precisely for this purpose. I'll apply that tommorow (On a piece of scrap first) to make sure the same problem doesn't occur. Failing all, I could use a water based varnish as an alternative - but as the two lounges will be used for social events including belly dancing, etc. I'd prefer the wood was as protected as possible with several coats of super hard Polyeurethane satin varnish.
I'm sure we'll work it out. Just one of those challenges that are sent to test us.
Here's another quote I recently enjoyed from Ann & Alex, our missionary friends in Cambodia.
“If you have a great ambition, take as big a step as possible in the direction of fulfilling it. The step may only be a tiny one, but trust that it may be the largest one possible for now.”
—Captain Mildred H. McAfee