Wet Abrasive Scrub, Surface Preparation (video)
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johnleeke
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Joined: 20 Aug 2004
Posts: 2972
Location: Portland, Maine, USA

PostPosted: Wed Mar 31, 2010 5:29 pm    Post subject: Wet Abrasive Scrub, Surface Preparation (video) Reply with quote

(updates: 12/20/13, scrub pad sources; 10/2/2012, tool list)


Video: 3 minutes.

We often use the wet abrasive scrub method to clean and prepare old paint and wood surfaces for painting. The cleaning solution is made of a powerful detergent like TSP Substitute or Dirtex, mixed in water according to directions. Then we add 20% by volume of ordinary household bleach. The scrubbing tool is the 3M Heavy Duty Stripping Tool, a reusable plastic handle with a 3-1/2" x 5" surface with Velcro-type hooks. The hooks hold a replaceable pad, the 3M Heavy Duty Stripping Pad, which has an open weave with abrasive grit. With this method personal protection is very important. We wear loose fitting long pants & shirt sleeves, long rubber gloves, respirator, splash goggles & face shield to prevent cleaning solution from getting on skin due to splash back. Sometimes a light rain suit with long sleeves and pants is necessary.
We dip the scrubbing pad in the cleaning solution and scrub the bare wood surface of the spot and the surrounding paint surface. Scrubbing briskly with force for 15 to 30 seconds cleans the surface and abrades away loose weathered wood fibers. Scrubbing longer than that is not good, because the wood is softened by cleaning solution and the longer it is wet the softer it gets. Then the wood is rinsed with water from the garden hose. When a hose is not available a garden pump sprayer can be used. Do not use a power sprayer, the high pressure can damage the wood and overload the wall with water.

The waste water has to be contained, controlled and disposed of properly. We usually do this with a "ground containment" made up of 6-mil plastic sheeting on the ground that drains into a 5-gallon bucket that is set into a hole in the ground. You can catch a glimpse of the ground containment in the video, although it is not explained in the video. (Check with your local health or environmental office for proper disposal methods.)

Then the painted surfaces and bare wood dry out thoroughly, which may take several days or a few weeks. (If you have a moisture meter you can use it to assure the wood is at or below 15% equilibrium moisture content.)

Tools


-- 3M™ Doodlebug™ Pad Holder 6472, for broad flat surfaces, 4.625 in x 10 in., with screw socket for standard painter's pole
Source: Amazon.com http://tinyurl.com/myx7omc



-- 3M™ Doodlebug™ Brown Scrub 'n Strip Pads 8541, 4.625 in x 10 in, 5/box
Source: Amazon.com http://tinyurl.com/8tj5kc8

-- Painter's Pole, 3' long, extends to 6', with standard screw threads on one end
Source: available at many local paint shops


-- 3M Heavy Duty Stripping Tool, for detail work, a reusable plastic handle with a 3-1/2" x 5" surface with Velcro-type hooks. The hooks hold a replaceable pad.
Source: NewEgg: http://www.newegg.com/Product/Product.aspx?Item=04P-001E-00029)
-- 3M Heavy Duty Stripping Pads, 3-1/2" x 5", made to fit the Heavy Duty Stripping Tool above.
Source: http://www.amazon.com/3M-10111NA-Heavy-Stripping-Surfaces/dp/B0007UVFWK

-- Hose and nozzle, for rinsing, Source: local hardware store

-- Bucket, for mixing and applying cleaning solution, Source: local hardware store

-- Personal protective equipment: goggles(splash rated), rubber gloves, face shield, rain suit, hat

Materials

-- Water
-- Bleach, household
-- Detergent, TSP Substitute or Dirtex
-- 6" aluminum flashing
-- Metal push pins, to hold flashing to siding

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John

by hammer and hand great works do stand
by pen and thought best words are wrought


Last edited by johnleeke on Wed Dec 10, 2014 4:05 pm; edited 12 times in total
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sschoberg



Joined: 29 Oct 2008
Posts: 568
Location: Plymouth, Indiana

PostPosted: Wed Mar 31, 2010 9:20 pm    Post subject: Reply with quote

Of course while using this procedure, you must catch the lead contaminated water and dispose it per regulations. Must not contaminate soil .
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johnleeke
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Joined: 20 Aug 2004
Posts: 2972
Location: Portland, Maine, USA

PostPosted: Thu Apr 01, 2010 6:30 am    Post subject: Reply with quote

You are correct, sir.

The waste water has to be contained, controlled and disposed of properly. We usually do this with a "ground containment" made up of 6-mil plastic sheeting on the ground that drains into a 5-gallon bucket that is set into a hole in the ground. You can catch a glimpse of the ground containment in the video, although it is not explained in the video. (Check with your local health or environmental office for proper disposal methods.)

_________________
John

by hammer and hand great works do stand
by pen and thought best words are wrought
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johnleeke
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Joined: 20 Aug 2004
Posts: 2972
Location: Portland, Maine, USA

PostPosted: Tue Oct 08, 2013 10:35 am    Post subject: Reply with quote

See the Pre-Treatment discussion here:

http://historichomeworks.com/forum/viewtopic.php?p=6257#6257

I started developing these pre-treatment methods back in the 1980s,
based on studies at the Forest Products Laboratory and my own experience.

If the paint is lifting off down to bare wood the main cause is
excessive moisture in the wood. The source of the moisture may be from
inside the house, or from rain water seeping in through joints in the
woodwork, or through cracks in the paint film.

Extreme Prep:
If the existing paint film is thicker than .015" (a dime is .023"
thick), then it is thick enough that the water vapor cannot easily
escape from the wood directly through the paint film, so it simply
pushes the paint film off the wood on its way out. When we want to get
the maximum durability of the new paint coating we remove all the
existing paint down to bare wood. We also clean the wood with a Wet
Abrasive Scrub:

http://historichomeworks.com/forum/viewtopic.php?t=1751

Durability:
With the combination of 1. Removal of heavy paint buildup, 2. Wet
Abrasive Scrub, and 3. Pre-Treatment, plus experienced and skilled
workers we have been able to get 20 to 30 years of life out of a paint
job. With an extreme salt water micro-climate that drops down to 15 to
20 years.

Sealing the Wood:
>>It seems to me that sealing the wood would reduce the opportunity for
the primer to soak into he wood for more "bite."<<

An effective pre-treatment should not seal the wood. It should leave
most of the wood cells at the surface open so the primer can still make
a mechanical bond by soaking into the cells. About 40% of the bonding is
mechanical and 60% of the bonding is chemical. The pre-treatment
improved chemical bonding by making the highly variable surface
conditions of old wood more consistent and suitable for better
performance of the primer.

_________________
John

by hammer and hand great works do stand
by pen and thought best words are wrought
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