Primer peeling off veneer plaster
John Leeke
Last year, I installed some very elaborate Bradbury and Bradbury ceiling
paper in my dining room. This ceiling of this room had been badly cracked
and was in terrible shape, so the previous owners had the plaster covered in
gypsum board. Several months after the paper was hung, I noticed that it
was becoming loose. Upon closer examination, I found that the paper had
completely peeled the original primer off the gypsum boards, all the way
down to the paper covering. Apparently, the contractor had used the wrong
primer, or perhaps had failed to clean the dust off the boards prior to
priming.
I scraped all the paper and the original primer off the ceiling. My
plasterer then cleaned it, coated it with Plaster-Weld, and the did a veneer
coat of gauging plaster, which according to him is lime based. He used STAR
brand made by USG, and the veneer was no more than 1/16th of an inch thick.
The plaster was allowed to dry in well heated and ventilated room for ten
days.
I consulted the Preservation Brief 21 on plastering, and under the section
"A Modern Replacement System" it addressed the issue of veneer plaster. It
said that it can be painted almost immediately after drying. I also asked
my plasterer who said the same thing.
After ten days, I primed the ceiling with Benjamin Moore brand Alkyd primer
which is formulated for porous surfaces, including plaster. However, even
after a whole week of drying, I was able to peel the primer off the ceiling
with low adhesion masking tape. The primer just didn't seem to bond with
the plaster at all. I tried the same primer on another porous surface, and
it adhered just fine.
I have finally taken down all the gypsum board and I'm going to start from
scratch.
I was wondering if you'd know why the Alkyd would fail to adhere to the
gauging plaster. I suspect that we didn't let the ceiling "cure" long
enough, but several plasterers said that ten days is more than enough, as
did the Preservation Brief. Are there chemical reactions which take place
in gauging plaster even after it's thoroughly dry? Is the curing of plaster
something different from thorough drying? If the plaster is dry after two
days, does something else take place in the next 30 days that would make the
paint penetrate and adhere properly?
--
John Leeke, Preservation Consultant
publisher: Practical Restoration Reports
contributing editor: Old-House Journal
website: www.HistoricHomeWorks.com
GYPMAN
John Leeke wrote in message ...
>I am stumped by the following question from a reader. Can you help?
>
>Last year, I installed some very elaborate Bradbury and Bradbury ceiling
>paper in my dining room. This ceiling of this room had been badly cracked
>and was in terrible shape, so the previous owners had the plaster covered
in
>gypsum board. Several months after the paper was hung, I noticed that it
>was becoming loose. Upon closer examination, I found that the paper had
>completely peeled the original primer off the gypsum boards, all the way
>down to the paper covering. Apparently, the contractor had used the wrong
>primer, or perhaps had failed to clean the dust off the boards prior to
>priming.
>
>I scraped all the paper and the original primer off the ceiling. My
>plasterer then cleaned it, coated it with Plaster-Weld, and the did a
veneer
>coat of gauging plaster, which according to him is lime based. He used
STAR
>brand made by USG, and the veneer was no more than 1/16th of an inch thick.
>The plaster was allowed to dry in well heated and ventilated room for ten
>days.
>
>I consulted the Preservation Brief 21 on plastering, and under the section
>"A Modern Replacement System" it addressed the issue of veneer plaster. It
>said that it can be painted almost immediately after drying. I also asked
>my plasterer who said the same thing.
"Veneer plaster" is not the same as gauging plaster. Gauging plaster does
not contain lime,
but should be mixed with lime before being applied.
If your plasterer had used veneer plaster, from USG or any other brand, you
could have
painted immediately, after it had dried. Lime - gauging is the old fashened
finish for full
thick plaster systems and is meant to go over sanded base plaster. In the
past they used to
recommend leaving the lime putty unfinished for a year. Lime takes a long
time to cure.
Chemically it is Calcium Oxide (CaO) and is very alkaline. Over time it
absorbs Carbon Dioxide
(CO2) from the air to form Calcium Carbonate (CaCO3). Until the alkalinity
is reduced most
finishes will not adhere well.
If your plasterer did not mix lime with the gauging plaster, I have no idea
why
the paint did not adhere. Did you contact Benjamin Moore?
>
>After ten days, I primed the ceiling with Benjamin Moore brand Alkyd primer
>which is formulated for porous surfaces, including plaster. However, even
>after a whole week of drying, I was able to peel the primer off the ceiling
>with low adhesion masking tape. The primer just didn't seem to bond with
>the plaster at all. I tried the same primer on another porous surface, and
>it adhered just fine.
>
>I have finally taken down all the gypsum board and I'm going to start from
>scratch.
If you are going to refinish the cieling with veneer plaster, use veneer
base (blue board)
instead of regular gypsum board, then finish with veneer plaster, not
gauging plaster.
Then you won't need Plasterweld, and you should be able to paint as soon as
he plaster
has with water based paint the next day. If you use an alkyd paint, allow it
to dry thoroughly
before painting.
George Green, gypsum consultant
Rutgersgrp
cement has to fully hydrate. Sometimes you can push the envelop by waiting on14
days. Waiting 28 days allows the cement to fully hydrate. Cheers:)
Spinman
Rutgersgrp wrote in message <19990303055625...@ng128.aol.com>...
I would agree with you if it was a Concrete slab for the 28 day curing time,
remember that the coat is only a 1/16" thick, 10 days is plenty of time.