I put the first coat of poly on my desktop and it looked fine. Here are
the facts pertinent or not:

1. Thinned about 10% with Low odor Mineral spirits from HD. - Minwhacks
poly.
2. Applied at 66 degrees with 8# pressure HVLP .041 tip.
3. Looked fine and dried enough in 4 hours to sand lightly with 220
grit, per instructions on poly.
4. Wiped off surface with mineral spirits (damp) and wiped again with
dry rag.
5. Applied second coat with same parameters as above.


On the first 3 pieces I sprayed, there were obvious little pinholes in
the film that weren't there during the first coat.

QUESTIONS:

I'm sort of suspecting the sandpaper. It is Norton's new line of 3X 220
grit. It's yellow and very flexible. Even though it says it's for
between coat sanding, I'm wondering if it has sterates in it. It says
nothing about sterates, but wouldn't that cause pinholes in poly?

I JUST WENT TO THEIR WEB SITE AND FOUND OUT THERE ARE STERATES IN IT.
WILL THAT SCREW UP THE FINISH??

Oddly, the last thing I sprayed was the desk top and it didn't look like
it had pinholes in it. I sprayed a bit onto scrap before spraying the
project, in order to set the spray pattern and volume. Even so, COULD
poor mixing of poly and thinner in the gun cause the first few items to
have pinholes? I resprayed them again and still could see pinholes.

What do you think went wrong?

Can I fix this for the next coat by using naptha or some other solvent
as a final wipe instead of mineral spirits?? What solvents would be safe
and effective for between coats?

dave

I have included a post from 1997 that may be useful for this and other
finishing problems. Specifically, the pre-fill in number 6 applies to
timbers such as oak, which, IIRC, is what your desk is made from.

I would be surprised if Nortons sold a paper that affect finishing after
sanding (not saying it's impossible, just unlikely) and suggest you look at
other possible causes first.

Greg

From: ersatz name )
Subject: Factory Furniture Finishing (LONG POST!)
Newsgroups: rec.woodworking
Date: 1997/08/21

I am not the author of this information. I did edited it somewhat. This
information comes from one of the big makers of furniture that you can buy
in
the stores.

This is what, how and why they do what they do in the furniture factories.
Many of the phrases and jargon will become more comprehensible as you
continue
to plow through this outline.

I find this inside look at the furniture industry fascinating. I have not
seen
ot printed or posted elsewhere. I hope that it helps to instill a greater
appreciation of the new furniture that you see in the stores in all of you
who
care to read this. Also, I hope that this information is useful, and at very
least interesting.
----------------------------------------------------------------

1. EQUALIZING

Objective: To reduce color intensity of varied woods.

Due to various reasons (price, seasoning, drying, etc.) all woods
entering finishing rooms are not the same color. Any abnormal color in
the wood must be neutralized. Example: a green pigmented type material
to tone down the redder woods and a yellow orange toner to tone down the
blue, gray and darker woods.

This operator generally spends half of his/her time looking, and the
other half spraying. Equalizing is a judgmental process and
special care should be taken in training this person. Improper
application can result in a wider variation in color within individual
pieces, rather than a general blend. Poor application can also result in
a painted appearance.
----------------------------------------------------------------

2. SAP STAIN

Objective: To bring varied colored woods to an overall average color.

Sap stain is generally used used on the lighter wood to bring it closer
in color to the average. In many cases, special saps are needed to
blend various species of wood together in the same piece of furniture.

Care should be taken in this operation so as not to undo what the
equalizers have accomplished. Again, the spray operator need not spend a
majority of his/her time spraying, but rather spend more time in being
effectively selective.

Following correct equalization and sapping operations, a piece of
furniture should blend better as far as overall appearance and color.
----------------------------------------------------------------

3. OVERALL BODY STAIN

Objective: Establish undertone color.

Consistent stain application is of utmost importance. Care should be
taken to insure that the operator has sufficient time to apply a good
uniform coat of stain. Each piece should receive a good uniform wet coat
of body stain.

Comment: more off color furniture can be traced to above operations than
any other in system. It is imperative to have good step panels at these
operations.
----------------------------------------------------------------

4. WASHCOAT

Objective: Seal off stain and provide smooth base (after sanding) for
subsequent operation. Consistent spray procedures are essential in this
operation.

A close check on washcoat should be kept as any change in white wood
sanding or bad spray technique will effect the bite of the wipe.

Special consideration should be given to turnings and end grain. These
may be sealed with a sealer before or after washcoat. This is most
important on soft[er] woods such as pine and maple. Care should be
taken to prevent spraying material on surfaces that do not require it.
This causes clean light areas where the wipe coat does not bite
sufficiently.
----------------------------------------------------------------

5. WASHCOAT SANDING

Objective: To prepare surface for finish wipe coat operation.

This step is important since it is the first finishing operation leading
to a good build and smoothness in the final film. Sufficient sanders
should be provided to insure smooth surface. If this operation goes
through rough it not only effects color but also makes sealer appear
rough and needing more sanding.
----------------------------------------------------------------

6. PRE-FILL

Open grain woods (oak, pecan, etc.) should be pre-filled with a paste
filler mixture to fill the pore. This operation helps the rub room rub
the tops to a uniform flat surface, rather than being open and hungry.
The actual application is usually done with a brush, rag, or a sponge.
Once filler is applied, it needs to be forced into the pore with a
circular motion using a pad wheel. This operation will prevent pinholes
when done properly.
----------------------------------------------------------------

7. INERT GLAZE

Objective: To provide a cleaner more uniform finish.

This material is applied selectively to areas where the fill glaze might
"bite in" and cause darkness and/or dirtiness. Once again, care should
be taken to apply this only to those areas that need it (end grain,
turnings, etc.). Careless application will result in unwanted lightness
in areas that did not need inert.
----------------------------------------------------------------

8. FILL GLAZE

Objective: To provide color and depth to finish.

With correct sanding and washcoat application the first wipe can
generally be wiped fairly clean. The first wipers generally break the
wipe down and work in, into the pore. These same people can also help
prevent black turnings and end grain by giving them attention first.
Generally speaking, tops should be wiped last.

The next wipers will finish cleaning up the cases. Many times a glaze
brush will help remove excess material from cracks, grooves, and
corners. This also adds a blending affect. This is a good time for an
inspector to make sure that all fill glaze is wiped evenly and removed
properly.
----------------------------------------------------------------

9. HIGHLIGHTING OF WIPE COAT

Objective: To enhance the grain of the wood and design features.

Highlighters should be aware of any special effects needed for the
particular piece of furniture such as wearing of corners, etc. At times
sandpaper is needed for depth of highlight, at other times steelwool
will give a softer look. Care should be taken not to pull filler out of
the pore on open grain wood with steelwool.

Again, it is important to compare highlighting techniques. Highlighters
should look for interest areas in the wood and bring these out; knots,
cathedrals, crossfire, dark moldings, etc. Wear highlighting is more
pleasing to the eye, but finger highlighting is easiest, therefore, for
the best appearance wear highlighting should be used. It is important to
compare highlighting techniques in production to those on the color
sample.
----------------------------------------------------------------

10. SEALER

Objective: To prepare surface for topcoats.

Sealers are higher in solids than washcoats Good sealer application
means a good foundation for topcoats. Good spray techniques and sealer
flow are imperative.
----------------------------------------------------------------

11. SEALER SANDING

Objective: To prepare antiquing and dimension to finish.

This operation is very important as it will determine how smooth and
clean the glaze operation will be. Poor sanding leads to dark and dirty
"bite in" areas in glaze operation. Good sanding leads to good lay down
and flow of lacquer.

The importance of washcoat and sealer sanding is the most overlooked and
taken for granted areas in finishing in the furniture industry today.
----------------------------------------------------------------

12. SECOND GLAZE

Objective: To provide uniform color and depth to finish.

The second glaze should be wiped uniformly and brush blended to give an
overall uniform and pleasing appearance.
----------------------------------------------------------------

13. HIGHLIGHTING OF SECOND GLAZE

Should be done with steelwool to enhance grain of wood and design
features and give overall pleasing appearance. Special clean-up may be
needed to avoid any dark areas that detract from finish.
----------------------------------------------------------------

14. FIRST LACQUER

(see #18 TOPCOAT LACQUER)
----------------------------------------------------------------

15. SPRAY PAD

Objective: To provide color and depth in an aesthetic manner.

Pad stain should be sprayed uniformly like a body stain. The spray pad
is then mottled or highlighted with a damp alcohol rag for desired
depth of finish and to match approved color sample.
----------------------------------------------------------------

16. HAND PAD AND BURNISHING

Objective: To further enhance the grain and provide further aesthetic
value to the finish.

Hand pad is applied by hand with a rag shaped in the form of a fine pad.
The rag is wet to the proper degree and the stain is then applied
selectively to those areas to which it can be most advantageously done.
If this operation is to be of any benefit, it must be done by trained
and motivated personnel. This operation properly done will provide the
most beneficial aesthetic quality to the finish of any operations. Also,
if proper highlighting techniques are used in first wipe and spray pad,
much less pad is needed.
----------------------------------------------------------------

17. SHADE

Use as little as possible to uniform cases. Shade, like equalizer and
sap, should be applied to selective areas only.
----------------------------------------------------------------

18. TOPCOAT LACQUER

Objective: To provide build, protection and to bring out the beauty of
the wood and the finishing technique.

A. Air Spray: The fluid pressure and atomization pressure must
be properly established to provide most efficient application in
relation to product size, speed of conveyor and load. In addition, the
proper tips and needles should be used.

B. Airless Spray: The fluid pressure, tip size and fan width
should be coordinated to provide the most efficient application,
according to the product size, speed of conveyor and load.

Dry time between coats and after final lacquer is critical to provide a
well cured film. Should the film not be dried thoroughly, it can result
in hazing of the finish either during rubbing or afterward. Insufficient
curing will result in a drop in sheen after packing. Consequently your
products may look good going into the box, but will be too low in sheen
when opened at a later date. Also, insufficient curing will lead to
paper printing in the box.

Your topcoat of lacquer should be formulated to give you maximum build
and clarity. The build and smoothness of the topcoat adds considerably
to the clarity and brightness of the finish.
----------------------------------------------------------------

19. RUBBING

Objective: To obtain smooth feel and proper patina to enhance the
finish.

There are a multitude of rubbing options that can be used depending upon
the desired results. Listed below are the general principals or choices
involved:

A. The drier the lacquer film is, the cleaner and more stable will
be the final rub job.

B. The rubbing lubricant to use should be a vegetable oil as opposed
to petroleum.

c. Depending on the sheen and clarity desired the sandpaper used
should be in gradations so that each succeeding finer grit can remove
the scratches of the proceeding one, i.e., 400 followed by 500 rather
than 600. Also the finer grit you use the clearer will be your rub job.

D. Rubbing lubricant (even when using vegetable oil) should be kept
cleaned off the lacquer surface as much as possible to keep them from
permeating the lacquer film and then "blooming" back later causing a
haze.

E. Following cut down with lubricant and sandpaper there are a
variety of materials to use to uniform the sheen depending upon how high
a sheen you want. They are as follows:

Ultra-fine Scotchbrite
4/0 steelwool
Rottenstone and vegetable oil
Rubbing compound and buffing wheel
Rubbing compound and scotchbrite

F. After the above operation, the surface should be cleaned and/or
waxed with a soft cloth. (Do not use waste).

Good rubbing procedure is essential to producing quality looking
furniture. A good finish is just like any other craft, it depends upon
good workmanship throughout the entire process, beginning with the most
important process, good white wood sanding, which provides a good
foundation for the finish.
-------
 Daniel

NOTE: Send me your e-mail at "shafner at webspan dot net" taking out the
quotation marks and inserting the appropriate symbols.

/ `-' ) ,,,
| IU U||||||||[:::]
\_.-.( '''

Hi BAD,
I did a lot of reading when I first bought my sprayer and all though I
never experienced it in person, one author mentioned "Micro bubbles" in
poly. These would be caused by shaking not stirring the mix and would result
in pinholes. IMHO this James Bond kind on thinking is bull but then I have
been wrong before. Cheers, JG

Bay Area Dave wrote:

I put the first coat of poly on my desktop and it looked fine. Here are
the facts pertinent or not:

1. Thinned about 10% with Low odor Mineral spirits from HD. - Minwhacks
poly.
2. Applied at 66 degrees with 8# pressure HVLP .041 tip.
3. Looked fine and dried enough in 4 hours to sand lightly with 220
grit, per instructions on poly.
4. Wiped off surface with mineral spirits (damp) and wiped again with
dry rag.
5. Applied second coat with same parameters as above.

On the first 3 pieces I sprayed, there were obvious little pinholes in
the film that weren't there during the first coat.

QUESTIONS:

I'm sort of suspecting the sandpaper. It is Norton's new line of 3X 220
grit. It's yellow and very flexible. Even though it says it's for
between coat sanding, I'm wondering if it has sterates in it. It says
nothing about sterates, but wouldn't that cause pinholes in poly?

I JUST WENT TO THEIR WEB SITE AND FOUND OUT THERE ARE STERATES IN IT.
WILL THAT SCREW UP THE FINISH??

Oddly, the last thing I sprayed was the desk top and it didn't look like
it had pinholes in it. I sprayed a bit onto scrap before spraying the
project, in order to set the spray pattern and volume. Even so, COULD
poor mixing of poly and thinner in the gun cause the first few items to
have pinholes? I resprayed them again and still could see pinholes.

What do you think went wrong?

Can I fix this for the next coat by using naptha or some other solvent
as a final wipe instead of mineral spirits?? What solvents would be safe
and effective for between coats?

dave

It would seem to me that atomization would free any entrapped air.

"JGS" wrote in message
...
Hi BAD,
I did a lot of reading when I first bought my sprayer and all though I
never experienced it in person, one author mentioned "Micro bubbles" in
poly. These would be caused by shaking not stirring the mix and would
result
in pinholes. IMHO this James Bond kind on thinking is bull but then I have
been wrong before. Cheers, JG

I didn't shake the can or the spray cup; I poured the poly from the
original can into the cup, added a bit of thinner and swirled them
together (only about 2" of material so it was easy to swirl). The
finish doesn't look like it has bubbles in it like when I've used
straight poly with a brush. That method always used to leave a lot of
entrapped air. This issue with the second coat of "pinholes" are very
tiny pin prick sized depressions with no surrounding gentle depressions.
AND of the 4 drawer fronts I sprayed, the first two were the worst,
the third is so-so, the fourth looks really good, and so does the desk
top which I sprayed after doing the drawers.



dave

JGS wrote:

Hi BAD,
I did a lot of reading when I first bought my sprayer and all though I
never experienced it in person, one author mentioned "Micro bubbles" in
poly. These would be caused by shaking not stirring the mix and would result
in pinholes. IMHO this James Bond kind on thinking is bull but then I have
been wrong before. Cheers, JG

Bay Area Dave wrote:


I put the first coat of poly on my desktop and it looked fine. Here are
the facts pertinent or not:

1. Thinned about 10% with Low odor Mineral spirits from HD. - Minwhacks
poly.
2. Applied at 66 degrees with 8# pressure HVLP .041 tip.
3. Looked fine and dried enough in 4 hours to sand lightly with 220
grit, per instructions on poly.
4. Wiped off surface with mineral spirits (damp) and wiped again with
dry rag.
5. Applied second coat with same parameters as above.

On the first 3 pieces I sprayed, there were obvious little pinholes in
the film that weren't there during the first coat.

QUESTIONS:

I'm sort of suspecting the sandpaper. It is Norton's new line of 3X 220
grit. It's yellow and very flexible. Even though it says it's for
between coat sanding, I'm wondering if it has sterates in it. It says
nothing about sterates, but wouldn't that cause pinholes in poly?

I JUST WENT TO THEIR WEB SITE AND FOUND OUT THERE ARE STERATES IN IT.
WILL THAT SCREW UP THE FINISH??

Oddly, the last thing I sprayed was the desk top and it didn't look like
it had pinholes in it. I sprayed a bit onto scrap before spraying the
project, in order to set the spray pattern and volume. Even so, COULD
poor mixing of poly and thinner in the gun cause the first few items to
have pinholes? I resprayed them again and still could see pinholes.

What do you think went wrong?

Can I fix this for the next coat by using naptha or some other solvent
as a final wipe instead of mineral spirits?? What solvents would be safe
and effective for between coats?

dave

Yes, George, the symptom is NOT like entrapped air which is what I get
if I brush unthinned poly.

dave

George wrote:

It would seem to me that atomization would free any entrapped air.

"JGS" wrote in message
...

Hi BAD,
I did a lot of reading when I first bought my sprayer and all though I
never experienced it in person, one author mentioned "Micro bubbles" in
poly. These would be caused by shaking not stirring the mix and would

result

in pinholes. IMHO this James Bond kind on thinking is bull but then I have
been wrong before. Cheers, JG

So, as another suggested, you may have the porous oak blowing bubbles from
below. Put the magnifier to it to see if the pinholes have a pore below
'em?.

"Bay Area Dave" wrote in message
m...
Yes, George, the symptom is NOT like entrapped air which is what I get
if I brush unthinned poly.

dave

George wrote:

It would seem to me that atomization would free any entrapped air.