I of course read the instructions fully before using it (didn't I? - oh!) so took all the necessary precautions to avoid any issues - but:
- It leaked. It shouldn't have - I had tested it with water several times, each time plugging all the leaks with waterproof PVA, varnish etc. It didn't leak that much but luckily most of the drips fell on the newspaper which was still down from the prior leak checks. I think one of the problems is it takes hours to set so has plenty of time to ooze through any tiny holes.
- There were very prominent meniscusses (menisci?) especially along the leat and around the viaduct piers. This was partly a result of wicking into porous scenery and vegetation (as noted in the instructions), and also possibly through loss of resin, i.e. the meniscus was the high tide and the level went down slightly through the leaks.
I tried to cover up the meniscus with vegetation but it was simply too prominent, and vegetation would not look right around the bridge piers etc. The resin sets to a rubbery state so it could not be easily scraped away - and it would probably have made it look worse. I eventually decided it needed a thin top coat. I reasoned that it had done any leaking and wicking that it was going to do, so this thin top coat should hopefully just fill the surface up to the top of the menisci. Of course I had now used up all the Magic Water.
A bit of late night internet searching showed there were several suitable clear resins - all quick setting which should enable corrective action to be taken during whilst it sets. I contacted Eli-Chem Resins UK who sold two types at a reasonable price. As a result of their helpful advice I ordered a General Purpose Clear Epoxy 350g starter kit - despite choosing their standard 5 day delivery it arrived the very next day!
I dribbled a thin coat into the middle of the leat and worked it into place with a spatula to just fill the meniscus. When it started to thicken up I carefully swept any build up away from the edges with a small coffee stirrer.
The result is much better. The top coat has set very clear with a hard glass like finish and the menisci are far less prominent. What remains can easily be hidden with some judicous planting.
(After planting - clearly it now needs a hoover)