Dan,

     There is a simple and painless way to remove paint on an historic
     building: Peel-Away I, Dumond Chemicals, Inc., 1501 Broadway, NYC, NY
     10036, fax: 212-764-5762, e-mail: [log in to unmask] I have used it for
     historic buildings with consistent success. It is really great for
     environmentally friendly lead paint removal. It should take off the
     paint on your terne roof with no damage to the roof. But I have to
     wonder why you painted a terne roof in the first place.  -Grace

______________________________ Reply Separator _________________________________
Subject: Metal Roof Paint Prep Query
Author:  "dan becker" <[log in to unmask]> at internet
Date:    7/29/98 10:05 PM


Query:  How to best remove peeling paint from a terne metal roof prior to
repainting?

Background:  I have a mostly standing seam, some flat seam terne metal roof
on my 1926 domicile, installed between 1932-41.  Following the rehab
project 4 years ago, "John the Butcher" painted the roof using the product
of a local coatings manufacturer that had previously had a very good
reputation.  As it turns out, my roof was painted at the very moment that
they altered their formula [read: cheapened the stuff] before anyone knew
what was going on.  Paint on the house exposed to ultraviolet and weather
began massive and wholesale failure within 18 months.  The causes of this
failure were very well described in Mike Edison's valuable and instructive
recent tomes: my house is an Arts & Crafts period catalogue house, so the
paint colors I selected are all heavily-pigmented earth tones...the pigment
contents the vendor loaded into the base exceeded the CPVC, to quote Mike--

>2. Binders, fillers, pigments
>In pigmented coatings like paint, there is another critical element- - the
>solid particles used to impart hiding power and color. Formulators refer
>to the critical pigment volume concentration (CPVC) as the level of
>pigment at which there is essentially just enough binder (resin) to hold
>the dry film together. Some companies produce coatings with pigment
>contents higher than the CPVC, so there is too little resin to completely
>encapsulate and bind all the pigment particles. The upside is high
>permeability due to imperfect films. The downside is high rates of
>chalking and reduced moisture resistance.

Here's my dilemma: how do I best get the failing stuff off now in order to
repaint the roof?  I'm the general contractor, the subcontractor, the
supplier, the site superintendent, the rigger, and the laborer for this
one.  I'm reasonably confident that the specs will be adhered to.  Because
the quality of what is on there is a known notoriously bad film, I really
am loathe to leave any of it on the roof prior to repainting, lest the
stuff fail beneath my new stuff.

I am also loathe to think about the idea of having to manually wire brush
the entire roof.  So...any means of effectively automating this process
without using some mechanism that will puncture/damage the roof or me?

Your suggestions are welcome.  I have this image of some wonder device with
a rotating (not circular) drum of really stiff bristles, sorta like the
main bristle drum of those old timey street sweepers that had the two round
curb bristle discs out front, the rotating drum in the middle, and the
single tire for steering in the back.  Make a clean sweep of the roof.  I
can't image trying to do any kind of dry abrasive blasting to strip the
roof, nor does trying to do a pressure wash sound too smart.

____________________________________________
Dan Becker
Executive Director, Raleigh Historic Districts Commission

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