Question Re Spraying Cabothane Water Based Satin Poly

[RoyG]

I'm just having my first go at finishing a project with Cabothane Water Based Clear Satin PolyU. I've sprayed a few other brands of PolyU finishes (various oil based and some water based), and haven't come across a particular instruction that is included on the Cabothane Water Based can.

The instructions on the Cabothane Water Based PolyU can state that "when spraying, back brushing is recommended".

I'm guessing that "back brushing" is something like "tipping off" that I used to use when brushing oil based gloss paints many years ago - i.e. gently dragging an almost dry brush across the surface, along the grain, normally done to minimise brush marks. But I don't see how that technique would apply to spraying water based PolyU.

So, can someone please advise what the term "back brushing" means ?

Many thanks,

RoyG

[Enfield Guy]

My understanding of back brushing/ tipping off is as yours.

By the way, I've only used water based poly once, never ever again!!! The stuff I used went on white and dried sort of clear. I didn't like it at all.

Cheers
Bevan

[RoyG]

My understanding of back brushing/ tipping off is as yours.

By the way, I've only used water based poly once, never ever again!!! The stuff I used went on white and dried sort of clear. I didn't like it at all.

Cheers
Bevan

Bevan,

Thanks for that info Bevan. I did some more Googling after I'd started this thread, and found one detailed reference to Back Brushing or Tipping Off of sprayed water based PolyU. The Waterlox web site advises that their water based PolyU can be applied with either an compressed air spray gun, or an airless sprayer, and that if an air-less spray unit is used, then you should back brush after spraying each coat (no reason why was given). They advise that it is best to have a second person following behind the spray gun operator to back brush immediately, before the finish starts to dry too much. I checked the Cabot's web site, but I couldn't find much in the way of detailed info.

I did a test run today, spraying the Cabothane using a HVLP compressed gun. It went on very well, without dilution, and I didn't bother doing any back brushing. Out of the brands commonly available in AU that I've tried previously, the Cabothane water based PolyU seems to be the easiest water based PolyU to spray.

In the past, I've had similar problems to yourself, with a water based PolyU looking finish making the wood look bland. I overcome that problem by applying one coat of Ubeaut Shellac as a first coat (primer ?) over the wood. I then follow with three coats of PolyU, sanding lightly with 600 grit between each of the coats. The coat of shellac seems to add the colour that is missing with water based PolyU alone, and with the shellac as a "primer", the figure in the grain is highlighted nicely. The shellac primer coat also ensures that the water based PolyU doesn't raise the grain in the wood, as it would if was applied directly to the timber.

Water based PolyU has been my preferred sprayed finish for a while now. It sprays easily, and the guns clean up easily. You still need to use a mask, but there are no obnoxious fumes. There are minimal environmental concerns. And it dries quickly before any dust etc can land on the surface, which is important considering that the driveway is my "spray booth".

Thanks,

RoyG