Help please - marks under varnish on timber stair treads

Hi,

some marks have appeared under the varnish on our timber stair treads. My builder blames my stair installers that they have not wiped off the excess PVA glue quick enough. He reckons that there is some sort of UV stabiliser in the PVA glue (he mentioned Aquadhere?) that doesn't show up when the varnish is applied but as the surrounding varnish yellows in sunlight while the area with the PVA glue stays the same colour.

The stairs were varnished just before Christmas and I had a look at the stairs not long after that and the spots were already there. It's hard to get good photos of the marks, its easy to see near the balusters but there are also some marks in the middle of the stair treads.

My questions -
1. Is the builders explanation correct?
2. How can I get it fixed?
3. Who's fault is it? Painter/Stair Installers/Builder? Unfortunately I engaged the stair installers directly, so the builder is blaming then and saying he can't do anything about it and it's not the painters fault.

Your advice appreciated! The stairs are beautiful Sydney Blue Gum and the spots are right in front of you when you look at them from ground level so I'd love to fix them somehow.

NAT

Attachment 87861

Attachment 87862

that looks terrible. Have you paid in full?

No haven't paid the stair case people in full yet, nor the final payment to the builder. But whose fault is it, and what can they do to fix it?

Who stained/treated/painted the balusters? (The vertical white pieces). I suspect that this is where the problem lies. They seem to have been treaded with a whitewash of some sorts. This may be what your builder is refering to. Look closely at how they have not been 'cut in" very well, ie there is a difference in colour at the base of the balusters, but obviously treated with some product after construction. Not sure what step came first, the varnishing or the whitewash.
Hope this helps.
George

Hi George, the balusters and risers haven't been painted yet. The builders painter baulked at the amount of cutting in required, as I wanted the stair treads and handrail varnished but the balusters, risers, stringers etc painted semi-gloss white - so I'll end up doing that part myself.

looks like a poor surface prep, suggest bare sand to raw wood then reseal.
end of the day its a defect so who ever did the clear coat and sanding should sortit

George, i actually think the cutting in issue you see could be varnish from the treads on the white wood. But i'm sorry Nat i don't have a better idea of whose fault it is but suspect it is the stair makers/installers if indeed they used glue. Furniture makers for example are very careful to remove all excess glue, and will even mask to prevent it where it shouldnt be, so, yeah it could be PVA. But the marks on the front of the treads are especially clumsy IF that is the case...

Edit. also agree with Gaza. the surface prep should have eliminated all contaminants, so doesnt really matter if it is glue or not. I suspect sandng back to raw will be difficult in the tight places without making more issues that may only become evident when the gloss is reapplied.

Hi r3nov80r & Nat,
good detective work. I misread the "cutting in" process when I looked at the pics. If the risers have not been painted I would suspect glue contamination. PVA glue is water based and does cause this type of stain under varnish. Just be calm when discussing the issue with all involved, especially if you have a lot of work to do. I have done similar when using water based glues or wood fillers under varnish type coverings, you just don't see the problem until the varnish starts to dry.
Selleys Aquadhere Interior - Specialist Adhesives | Selleys Australia
The cutting in skills of the varnishers presents an additional small problem.

Thanks for the tips guys. The painter reportedly did sand everything back before application etc, the builder reckons the glue isn't removed by sanding though and isn't visible after sanding. I'm not sure if that's the case as I didn't see it prior to the application of the finish. Anyway I'll go back to the stair installers and ask the question of them as well.

Nat, your builder may well be right. A light sanding will not eliminate the glue, nor will anyone be able to see any difference on the wood where the PVC was once smeared.

Thanks George. If that is the case, then can anything be done to fix this? If a light sand won't eliminate the glue, is it possible to sand it heavily enough to tell if the glue has been removed before varnishing again?

Update: I followed up with the stair installers and they would like to come and have a look, so I am hopefully meeting them there this afternoon, they admit it looks like glue too.