My efforts continue to create a glossy lacquered finish on a piece of
After my previous experiments it became clear that I would need to
fill the grain with something before applying lacquer. To verify this
I tried using some "natural" grain filler, and the result was nice and
smooth and quite glossy:
But for the real thing I needed something transparent, as the presence
of the "natural" grain filler was very obvious. So I bought some
clear cellulose sanding sealer. After 3 coats of this the wood was
looking quite good, from a distance and in the right light:
I was hoping that I would be able to sand that and then spray
lacquer. Unfortunately, from close up and especially after sanding,
many small bubbles are visible in the grain:
These bubbles weren't evident immediately after applying the sanding
sealer. It's possible that I wasn't looking carefully, but I also
wonder if air from deeper in the grain has risen while it was drying.
Or perhaps it is because I had wiped the wood with white spirit
("mineral spirits") beforehand, and its vapour has come out of the
wood under the sealer.
Any suggestions, anyone?
Could be if your "white spirits" actually were mineral spirits (AKA "paint
thinner" in the US) and not alcohol. If it *was* alcohol, I can't see it
causing a problem as it doesn't leave a residue as does paint thinner.
To mitigate your problem, I would spray on a fairly wet coat of *lacquer*
thinner - assuming that is the thinner for the sanding sealer - so it can
melt the bubbles. When completely dry, use more sanding sealer if needed;
if not, go to regular lacquer.
UK "white spirit" = US "mineral spirits" = comes from oil
UK "methylated spirits" = US "de-natured alcohol" = ethanol
That's an interesting idea. I have some cellulose thinner in a
bottle, but no good way to spray it. I'll try to improvise something;
the worst that can happen is that I have to sand it again.
It's not very visible until I sand it. My feeling is that it will
remain clearly visible if I now lacquer it. Perhaps if I now apply
more coats of sanding sealer, then sand, then lacquer it will be
harder to see. But I will still _know_ that it's there...
Your sealer is quite probably lacquer with talc in it. If you scratch a
piece of talc, you get a white scratch mark but once wet again the white
In my previous incarnation I was a photographer. In order to retouch color
prints they need a "tooth". That tooth could be applied via spray cans of
retouching lacquer but they weren't cheap; always ascribing to the "a penny
saved is a penny earned" adage I started making my own - talc in lacquer.
Upon spraying same, I would sometimes get very small, white flecks where the
spray had built up around a piece of dust or the like. They disappeared
when sprayed with regular lacquer after retouching.
First guess would be out-gassing while drying.
Beyond making sure all volatiles have dried, and testing for
chemical compatibility before sealing something,
temperature control will play an important part in fine finishing.
The trick is to spray while the surface is cooling - not warming.
Carefully note the "ing"s there. I'm talking about the temperature
of the surface changING - not a static temperature.
If the surface is getting warmer while the coating dries/cures
then you often see tiny gas bubbles form in the varnish/epoxy
On 10/15/2011 10:29 AM, Phil Endecott wrote:
That's possible; I have mainly been doing this outside, for
ventilation, and temperature will have changed significantly over the
course of the day and night.
So perhaps if I keep it inside in the warm, then take it outside to
apply the sealer mid-day, and leave it outside for the afternoon/
evening to dry, I will get better results.
Thanks for the suggestion.
Mine works the other way - outdoors to warm it up, and bring it in to
But being aware of which way the temperature is going seems to have been
Best of luck, Phil.
Was this wood previously finished? If so, you might be seeing a reaction to
the residual finish lodged in minute dents in the wood. One solution is to
sand the heck out of the surface to get the surface below even the tiniest
dent. Another, easier, solution is to wipe the surface with a series of
sovents. My table did the same thing until I hit it with Xylene (this was
after Mineral Spirits, paint remover, alcohol, and anything else I could
The sanding sealer is attacking the filler because it
has a more active solvent. Try pumice as filler next time.
Apply a couple of spit coats of dewaxed shellac
(lacquer won't stick to wax), sprinkle with 4F pumice,
then rub in with an alcohol-dampened pad.
Once the pores are filled, you really don't need a
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