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9th June 2016, 10:32 AM #1Novice
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Dreaded "Fish-eye" in brushed polyurethane finish.
G'day.
I have been afflicted with the dreaded "fish-eye" problem when finishing 20-odd small/medium table tops that I am re-finishing for a customer.
Most of the tops are Jarrah veneer over chipboard, a few are solid Tas Oak, over which I have applied spirit stain and brushed on Wattyl poly. (new tins & brush so no contamination possible.) Every top developed little 5mm circles fairly evenly accross the piece, like little craters in the finish. I have ruled out contamination from the chipboard/veneer glue as it has also happened to the 3 solid tops.
I was able to flatten the finish & eliminate the fish-eye by "re-brushing" the surface with the wet brush twice (without applying any more poly.) This has left me with a sandable surface, but won't do for the final coat.
It has been fairly cold here (Melbourne) lately, which I am fairly certain is the culprit.
The temp in my work area has been around 15 deg C, which is above the recommended minimum of 10C. Getting the temp up, which will I'm quite sure will fix the problem, will be very hard as it is a large, reasonably poorly sealed room (8 x 5m, 3m ceiling w exposed & un-insulated gal tin roof.)
This happened to me once years ago when it was cold - I can't remember how I dealt with it.
My question is, has anybody used, or know of a "fish-eye inhibitor" for polyurethane?
Being veneer, these tops won't withstand another sanding so I've got one crack at it from here.
I think it may be time for me to set up a corner spray-booth again.
Cheers,
W.
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9th June 2016 10:32 AM # ADSGoogle Adsense Advertisement
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9th June 2016, 11:26 AM #2
Two possible causes come to my mind. Yes the cold but may be water vapour in the air, then the other is.....the dreaded Mr Sheen, Silicone on the surface. Warmer dryer air will fix it if that is the cause but for the Mr Sheen....big wash down with solvent
Just do it!
Kind regards Rod
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9th June 2016, 12:01 PM #3Novice
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- Mar 2009
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- Melbourne
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Thanks chambezio,
Can't be Mr Sheen as the tables were stripped/sanded/stained.
Now that I think about it, it wasn't freezing when I coated them, but look at the humidity reading on the attached BOM chart for that time of day on 07/06/16. Wet air alright.
BOM June 7.jpg
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9th June 2016, 12:10 PM #4
Ah!! one has to look at "de facts" like Hercule Poirot. Another manifestation of moisture when spraying lacquer id "blooming", moisture gets trapped in the coat and looks like a white haze on the surface.
Just do it!
Kind regards Rod
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9th June 2016, 12:16 PM #5Novice
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- Mar 2009
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- Melbourne
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- 23
Bloody Melbourne climate!!
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9th June 2016, 02:36 PM #6SENIOR MEMBER
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Don't discount silicon contamination (from Mr Sheen or similar products). Stripping and sanding won't always get all the silicon out, especially if the owners have religiously cleaned and polished those table tops with Mr Sheen for years and years. One coat of Clear De-waxed Shellac (clear so you don't change the timber colour, and de-waxed so that the top coats of poly will stick securely) will seal in any silicon and any other contamination, and pretty much any finish will go over the Shellac without problems.
RoyGManufacturer of the Finest Quality Off-Cuts.
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9th June 2016, 10:31 PM #7Taking a break
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- Aug 2008
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- Melbourne
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Don't know if it'll help with your specific problem, but foam rollers are great for getting an even finish with poly - probably faster than brushing as well.
If you want to have a crack at sanding, we have a calibrating wide-belt sander at work accurate to 0.1mm. I've run veneer board through it many times (some jobs worth several thousand dollars) and have 100% confidence in it
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9th June 2016, 11:22 PM #8
Can't speak for poly, but this time last year I was spraying shellac on a job and got blooms. On one particular day they were so bad the surface looked nearly white. It just so happened the blooms disappeared after a few hours (perhaps the next day) as the moisture escaped. As for fish eye .. ???
Glenn Visca
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10th June 2016, 12:14 PM #9Novice
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- Mar 2009
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- Melbourne
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Thanks guys.
It's funny Roy, I didn't get on the pc until late in the day, but a couple of hours after you posted about dewaxed shellac, I was discussing the problem with my old man, who suggested just that. He's been at this caper twice as long as the 20 years I have. Unfortunately, by then I'd got a second coat on a few tops before they started to "orange peel" rather than fish-eye, trying to take the first coat with it. They will sand flat fortunately. The rest have now been nicely sealed with shellac, and are ready for a light sand, then on goes the final coat of poly. Thanks for your advice.
I did get a bit of bloom in the 2 coats of brushed shellac yesterday, Glenn.Visca, but like your experience, they vanished within a couple of hours luckily.
Thanks for the tip elanjacobs - I'll give the rollers a go on the next job - don't want to temp fate with this one. I'll be in touch re your WBS re a different project.
Cheers.
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10th June 2016, 06:24 PM #10
It sounded to me like condensation. Insulation or sarking under your gal tin roof could prevent a repeat.
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10th June 2016, 07:49 PM #11Novice
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- Mar 2009
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- Melbourne
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My work area has more gaps than a barcode! Something to work on ASAP.
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14th June 2016, 12:14 AM #12New Member
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- South East Melbourne
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Hi coming from an spray painting background if it is silicone contamination, wiping down surfaces with say prepsol etc just moves silicone (hopefully onto the cloth ) we use a product called "silicone drops" in the 2 pak paint if there is a problem in the first coat. What does everyone wipe there dashboard down with ......Amour All !!!! Pure silicone. Cheers.
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