I have a wooden exterior door on my house (oak). I stained the door
and then put an exterior polyurethane sealant on it (5 coats).
Moisture must have gotten under the sealant because some black stains
have appeared under the sealant, to the point where it must be redone.

I'm in the process of stripping the polyurethane and that's going
pretty well.

My questions a

Once the sealant is off, does the door have to be sanded down to the
bare wood (remove all the natural oak stain that I originally applied?

How to remove the black stains?

What to reseal it with?

Any suggestions?

Stephen

P.S. We are in Florida, near the ocean (not the greatest location for
a wood door, but several neighbors have them, and they've been able to
have a wood door, as long as it was well sealed?

wrote:
I have a wooden exterior door on my house (oak). I stained the door
and then put an exterior polyurethane sealant on it (5 coats).
Moisture must have gotten under the sealant because some black stains
have appeared under the sealant, to the point where it must be
redone.


Red oak or white? Red Oak is porous and prone to rot and mildew.

There are at least wo kinds of wood bleach on the market. One is
oxalic acid, the other is a two-part bleach using sodium hydroxied
and hydrogen peroxide. I've tried both on red oak. The oxalic acid
didn't seem to do anything, the two-part bleach worked OK.

Shellac is reputed to be the best base coat to use as a moisture
barrier so that may be your best bet after you are down to bare wood.
For the best results it should be mixed fresh from flakes, see
http;//www.shellac.net. For second best results using pre-mixed
shellac check the date on the bottom of the can and use the freshest
you can find. If you use the 3 lb shellac from the can thin it
about 2:1 shellac to alcohol. Use dewaxed shellac.

Then you can go over the shellaced door with a good exterior
varnish.

Good luck.

--

FF

wrote:

I have a wooden exterior door on my house (oak). I stained the door
and then put an exterior polyurethane sealant on it (5 coats).
Moisture must have gotten under the sealant because some black stains
have appeared under the sealant, to the point where it must be redone.

I'm in the process of stripping the polyurethane and that's going
pretty well.

My questions a

Once the sealant is off, does the door have to be sanded down to the
bare wood (remove all the natural oak stain that I originally applied?

No, and it would be impossible w/ porous oak anyway unless you take off
an inordinate amount of material

How to remove the black stains?

Oxalic acid (deck cleaner)...

What to reseal it with?

Good quality exterior spar varnish...


Don't say where the staining occurred so can't do more than conjecture
on cause. Couple of possibilities are points of penetration of
hardware, a brittle former topcoat that fractured, a scratch that broke
the surface, a path under the topcoat around a door panel, ...

wrote:
wrote:
I have a wooden exterior door on my house (oak). I stained the
door
and then put an exterior polyurethane sealant on it (5 coats).
Moisture must have gotten under the sealant because some black
stains
have appeared under the sealant, to the point where it must be
redone.


Red oak or white? Red Oak is porous and prone to rot and mildew.

White oak.


There are at least wo kinds of wood bleach on the market. One is
oxalic acid, the other is a two-part bleach using sodium hydroxied
and hydrogen peroxide. I've tried both on red oak. The oxalic acid
didn't seem to do anything, the two-part bleach worked OK.

So you're saying that it would be better to go with a bleaching product
made specifically for wood.

My guess is that I'd have to apply it to the whole door, otherwise the
part where the stain was bleached would appear a different color, no?


Shellac is reputed to be the best base coat to use as a moisture
barrier so that may be your best bet after you are down to bare wood.

When you say down to bare wood, do you mean sanding off the stain, as
well. I've been able to get the polyurethane off using a poly
remover,and scraping it down. The wood still has the color that I
stained onto it when I began. I can only think that to get that color
off, I have to totally sand down the entire door. Is that necessary?
I just want to know. I will do what is required.

I have a wooden exterior door on my house (oak). I stained the
door
and then put an exterior polyurethane sealant on it (5 coats).
Moisture must have gotten under the sealant because some black
stains
have appeared under the sealant, to the point where it must be
redone.

I'm in the process of stripping the polyurethane and that's going
pretty well.

My questions a

Once the sealant is off, does the door have to be sanded down to
the
bare wood (remove all the natural oak stain that I originally
applied?

No, and it would be impossible w/ porous oak anyway unless you take
off
an inordinate amount of material

OK. thanks.


How to remove the black stains?

Oxalic acid (deck cleaner)...

I would apply it to the stains only, or the entire outside face.


What to reseal it with?

Good quality exterior spar varnish...


Don't say where the staining occurred so can't do more than
conjecture
on cause.

The stains were mostly on the lower half of the exterior, across the
entire bottom of the door, and near where a kickplate would go. The
door is covered by a portico so the top part is sheltered.

It did get a lot of exposure during the hurricanes last fall, so
seawater/rain/wind probably played a good part in all of it.
(We would have covered the door, but we weren't here.

Thanks for the tips.

wrote:
....
How to remove the black stains?

Oxalic acid (deck cleaner)...

I would apply it to the stains only, or the entire outside face.


Try it...probably will want to do the whole door to even it out. If is
effective against the particular stain (and I suspect it will be), it
will probably be fairly easy to get a reasonably good match.

....
The stains were mostly on the lower half of the exterior, across the
entire bottom of the door, and near where a kickplate would go. The
door is covered by a portico so the top part is sheltered.

It did get a lot of exposure during the hurricanes last fall, so
seawater/rain/wind probably played a good part in all of it.
(We would have covered the door, but we weren't here.

Probably a good plan/decision...

I'd say if it wasn't stained significantly prior to that time your
surmise is correct--the strong wind essentially did an accelerated aging
test.

If the black stains are oxidation from metal, which can be dust from
the grinder, to nails, lemon juice works well. Apply to the stain, and
let it sit, sometimes you have to leave it on overnight, and/or do
multiple applications.
robo hippy

wrote:

How to remove the black stains?

Got any iron/steel in the door? Fastenings, whatever... If so, remove
and replace with bronze best) or brass else the door will stain again.

--
dadiOH
____________________________

dadiOH's dandies v3.06...
....a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico

How to remove the black stains?

Oxalic acid (deck cleaner)...

I would apply it to the stains only, or the entire outside face.


Try it...probably will want to do the whole door to even it out. If
is
effective against the particular stain (and I suspect it will be), it
will probably be fairly easy to get a reasonably good match.

Just wanted to say thanks to all who posted their responses.
The oxalic acid worked great and the door came back better than
I thought it would. I applied it to the entire door. It did lighten
the color somewhat, plus the sun bleached it over the past year,
so I do plan on restaining it before resealing.

Thanks again.

Stephen







...
The stains were mostly on the lower half of the exterior, across
the
entire bottom of the door, and near where a kickplate would go.
The
door is covered by a portico so the top part is sheltered.

It did get a lot of exposure during the hurricanes last fall, so
seawater/rain/wind probably played a good part in all of it.
(We would have covered the door, but we weren't here.

Probably a good plan/decision...

I'd say if it wasn't stained significantly prior to that time your
surmise is correct--the strong wind essentially did an accelerated
aging
test.

writes:


[...]

I thought it would. I applied it to the entire door. It did lighten
the color somewhat, plus the sun bleached it over the past year,
so I do plan on restaining it before resealing.

Beware of darkening the door to much, because a dark door will get
hotter from sunshine than a light coloured one, thus aggravating any
aging effects.
--
Dr. Juergen Hannappel http://lisa2.physik.uni-bonn.de/~hannappe
Phone: +49 228 73 2447 FAX ... 7869
Physikalisches Institut der Uni Bonn Nussallee 12, D-53115 Bonn, Germany
CERN: Phone: +412276 76461 Fax: ..77930 Bat. 892-R-A13 CH-1211 Geneve 23

wrote:
wrote:
wrote:

....

White oak.


Good.


There are at least wo kinds of wood bleach on the market. One is
oxalic acid, the other is a two-part bleach using sodium hydroxied
and hydrogen peroxide. I've tried both on red oak. The oxalic
acid
didn't seem to do anything, the two-part bleach worked OK.

So you're saying that it would be better to go with a bleaching
product
made specifically for wood.

Yes. I'd only turn to chlorine bleach as a last resort.


My guess is that I'd have to apply it to the whole door, otherwise
the
part where the stain was bleached would appear a different color, no?


Maybe. I'd try it just on the black stains first and see what happens.
Even if the bleach does fade the color, you may be able to recolor it
with more stain. If the door is not too old it may match. Staining
wood twice supposedly does not change the color as the wood picks up
as much stain as possible on the first application.

But I can't ses your door. Problems near the bottom of the door
won't stand out like they would at eye level.


Shellac is reputed to be the best base coat to use as a moisture
barrier so that may be your best bet after you are down to bare
wood.

When you say down to bare wood, do you mean sanding off the stain, as
well.

No. A true stain doesn't really seal the wood.

--

FF