Guide to whole house paint removal and recoating.


Note:

On some projects, I've removed and reinstalled all 
the siding back side out... Click here for info.

Homeowner's checklist for a lifetime 
exterior paint job: rogcad.com/painting


Part I

Tools and techniques for using heat to completely remove
paint from siding and trim.

     1. Ground Cover
     2. Scaffolding
     3. Face Mask and Clothing
     4. Surface Preparation - Heat Guns
     5. Pro-Prep Scrapers
     6. Setting Nails
     7. Hand Sanding
  
Part II

Materials and techniques for coating bare wood.

     8. Soaker Coat
     9. Caulk
    10. Acrylic Primer
    11. Finish Coats
    12. Encapsulation
    13. Overpainting

   
  
  
  I've been painting old houses in Minneapolis since 1976, with 
  an interest in the longevity of the paint job.  I've done 100 
  percent paint removal and recoating on dozens of large houses, 
  most of them using heat guns, working by myself.  Click on the 
  image to see a house which was stripped using heat guns.

Part I

Paint removal

1. Ground Cover

    Protecting the health of your customers, their neighbors
    and their pets is the motivation for containing lead paint
    chips and dust.

    Cover the ground with 4 or 6 mil plastic sheeting, cutting
    and fitting tightly around bushes.  Hang nylon tarps over 
    bushes, and remove these each night.  Use plenty of ballast 
    to secure the ground cover.  After paint removal, slice it 
    into manageable sections and roll it up.

    Vacuum up any remaining chips using a wide diameter
    vacuum hose with a tapered attachment.  This will
    prevent clogging the hose with chips and twigs.

2. Scaffolding

    You'll be far more productive working off a plank 
    than off a ladder.  Every house scaffolds differently,
    and a lot of thought must be given as to exactly
    how to implement it.  Whether you rent or own your 
    scaffolding, you'll find adjustable stands and sidearms
    for planks to be very valuable accessories.

    Scaffolding will also provide a means for hanging 
    tarps to help direct chips and dust downwards to the
    ground cover.

3. Face mask and clothing

    The motivation here is to protect yourself with a mask,
    and to protect people and pets you come in contact with
    by changing clothes at the jobsite.

    I've been using charcoal canister breathing filters.
    These seem to be effective, since lead has a definite
    odor, and these filters block out all such odor.  There
    is a filter called ULPA (Ultra Low Penetration Air)
    which apparently is the ultimate protection against
    lead fumes, but don't look for it at your paint store.
    Eyes can also absorb lead fumes, so you might want to
    consider full face protection.

4. The heat gun

    

    I've carefully measured stripping progress using single, 
    double and triple heat guns, and consistently find that 
    double heat guns strip at exactly twice the rate of single 
    guns, and triple heat guns strip at exactly triple the rate 
    of single guns.

    Triple guns work well for siding.  I buy the twenty dollar
    guns at Menards or Home Depot, remove the plastic casing
    from two of them, and through the use of electrical or
    duct tape, achieve the configuration in the photo.  By 
    doing this and by fastening the cords at your waist, you 
    will reduce the weight to exactly that of two heatguns.

    A very important modification of the nozzle is to make about
    a dozen snips and flare out the resulting sections as shown
    in the photo.  This will not only spread the heat out more
    uniformly on the surface to be stripped, it will also allow
    you to hold the nozzles right up against the surface and 
    keep them there.  The biggest mistake workers make when 
    using heat guns is that they tend to keep backing the gun
    away from the surface.  The nozzles should rest on the 
    surface 100 percent of the time you are stripping.  

    Work in long strips.  Heat spreads through the paint film
    by conduction.  If you work in short strips, you lose this
    advantage of preheating.  You also lose this advantage
    every time you back the gun off the surface.  

    Double heat guns work well for trim and siding.  Simply tape 
    two guns together.

    Each heat gun requires a separate electrical circuit.  Have 
    lots of cord on hand.  Each 1000 watt gun costs eleven cents
    per hour to run.  Thus, a triple gun costs less than three
    dollars per day to operate.

 Fire hazards

    Heat stripping does not need to be a risky procedure.  The
    most important thing is to carefully caulk all cracks,
    holes and gaps between boards before using heat.  Carefully
    inspect under each siding board as well as all other boards
    for gaps, holes or cracks.

    Hidden fires in walls, eaves and under shingles start 
    in two ways:

      1. Heat flowing into cracks, holes or gaps.
                    
           There is very dry wood or even dry wood dust in
           walls, eaves, and at the roof line.  This can 
           begin to smolder without your knowledge and erupt 
           into flames after you've gone home.

      2. Sparks emitted from heat gun nozzles drift into
         cracks, holes or gaps.

           Bits of paint shavings fall into the nozzles and
           come out as sparks, particularly when melting on
           the underside of a horizontal surface, such as a 
           soffit, which at any rate is generally recommended 
           against.

    You can virtually eliminate the risk of fire by using caulk 
    to fill in any cracks, holes or gaps prior to heat stripping.
    This is my standard procedure.  Never aim your gun at or below 
    any crack, hole or gap.  

    One place that cannot be caulked is where the roof shingles
    meet the fascia board.  Stay well away from the roof line
    when heat stripping.  Dry scrape the upper few inches of 
    the fascia board.

    Whenever in doubt, turn the guns down to the low heat setting
    or back them well away from the surface and use a little extra 
    scraping muscle.

    Keep a water hose with nozzle attachment and crow bar near 
    you on your scaffolding. The hose should be left on at the
    spicket.  (A small fire extinguisher is very handy.)  In the 
    event of a fire, do not pry up any board until you have the 
    hose in hand.  Prying up a board gives the fire a burst of 
    oxygen and sudden life, causing it to spread rapidly.   


4.5 Infrared heat (radiant heat) for paint removal

    Another possibility to consider:

    A lightweight infrared heater using just one electrical
    circuit strips paint nearly as fast as my triple circuit
    heat guns, provided there is reasonable continuity of the
    paint film to be stripped.  I began using infrared heat 
    occasionally, beginning in 2004, after being alerted to it by 
    a reader of this website.  It's been a nice compliment to
    my old standby conventional heat guns.  The drawback is that
    there is a slow initial heat transfer to the substrate,
    meaning it is all the more important to keep the tool on
    the substrate continuously.

    There is no fire hazard to speak of, and little or no need 
    of a face mask.

    Why no one thought of this for paint removal 40 years ago is 
    hard to understand.  The technology is at least that old.

    There is a commercial model available, but I didn't want 
    to spend $465 on the heavy commercial model when I could 
    make a lightweight model for about $50 in materials and 
    30 minutes of my time.  I converted an old infrared room heater 
    for which I had paid about $50 into a very lightweight paint 
    remover.  The replacement tubes are only $10 (and I have yet to 
    burn out a tube).

    My tool works as well as the commercial model, based on 
    everything I've read about the testing others have done with
    the commercial model.  The working parts in my tool are the 
    same as in the commercial model - two quartz tubes.

    Go to wbmarvin.com for a listing of available infrared
    heaters and the $10 replacement tubes.  The model 5460 
    Steam 'n Heat at $79.95 looks like the current version of the 
    old Marvin heater I had used to make my paint remover.  You 
    might also check at Walmart or search online for inexpensive
    infrared quartz room heaters.

    Make your own infrared paint remover and save the weight and
    the high cost of the commercial model.  The commercial model 
    (Silent Paint Remover) weighs 4 lb 3 oz.  My infrared paint
    remover weighs just 1 lb 12 oz.  This includes the 12 oz
    clamp being used for the handle.  A lighter handle, such as
    a simple L shaped piece of wood will bring the weight down
    to just 1 lb 1 oz.   Having stripped paint for a living for 
    the past 40 years using heat guns, I can assure you that 
    you'll appreciate this weight reduction and increased 
    productivity.

    

    

    I refolded the aluminum reflector so that the tubes would
    be spaced 2 1/2 inches apart, which is the average spacing
    of narrow lap siding.

    I also made a single tube model for doing narrow architectural 
    detail.

    Neither the aluminum reflector or the clamp get too warm
    to cause any problem.  I casually lay the tool down facing
    up and running (meaning plugged in - no switch needed) when
    I'm not using it.  You can lay it down on any surface such
    as a wood plank, the ground, or a nylon tarp.

5. Pro-Prep scrapers

    

    These scrapers will not only greatly boost your heat stripping
    output, they will be your partner in all kinds of dry scraping 
    endeavors, from high speed outdoor dry paint removal to fine
    interior wood refinishing projects, including furniture.

    Proper sharpening and use of these scrapers is at the heart
    of indoor and outdoor refinishing projects.  The blades shown 
    above will be your primary ones for outdoor work (and most 
    indoor work).  For heat stripping, I use the small sized 
    handles even with the large sized blades.  This gives greater 
    clearance for shavings.  

    Buy large medium grade files by the half-dozen, or by the
    dozen if you have a helper.  A sharp file is the only tool
    to use to sharpen your scraper.  As soon as filing becomes
    a bit of a struggle, throw the file away.

    

    Place the scraper on a firm surface and file into the blade
    edge.  File at a 45 degree angle.  Slightly round the corners
    of the large flat blades as shown in the drawing, and for 
    dry scraping, very slightly arc the entire edge as shown.  
    Rounding the corners will help keep you from making gouge lines
    on the surface you're scraping.  Arcing an edge will give you
    better bite for dry scraping.

    Keep your file with you at all times.  Dry scraping necessitates 
    resharpening as often as every half minute.  Heat scraping 
    necessitates resharpening about every five minutes.

    Use a variety of motions with your scraper - towards the guns
    with the grain, away from the guns with the grain, perpendicular
    to the grain, and diagonal to the grain.

    Take your time and let the heat do most of the work, or
    you'll end up with gouges on your wood surfaces.  Clean up
    all residue as you go along.

    Heat assisted scraping is usually the best approach even
    when just spot scraping.  It's gentler on the wood and will
    allow you to feather the paint as you go along.
 
    Retire your blade as soon as it becomes a bit of a chore
    to sharpen it.  (You get to the thicker part of the blade
    as you sharpen it.)  The cost of the files and scraper
    blades is small compared to the cost of struggling with
    expended files and blades.

    

    Here is a great dry scraping tip for fast paint removal,
    especially when the paint is stubbornly attached:  Use the
    round edge of your blade to make channels in the surface.
    Space these parallel channels about 1/3 of an inch apart.
    Then come back over it with the flat blade.  Presto - you
    can strip any thick stubborn paint with very little muscle.
    The only catch is that it sometimes leaves a somewhat crude
    surface.  Be careful of where and how you use this technique.

6. Sinking nails

    Setting nails needs to be done after heat stripping and before 
    sanding.

    I found that I couldn't set nails for very long unless I used a
    vicegrips to hold the nail set, as my fingers gave out.  Better 
    yet, grind the ball of a ball-peen hammer into the shape of a nail 
    set.  Then use another hammer to strike the ball-peen hammer.  You 
    can really fly along with this method.  It's been my method for 
    the past fifteen years.

    

    The nail set holes are filled with a low shrinkage elastic
    filler after the initial wood priming.  A good general purpose 
    filler is CLEAR siliconized acrylic caulk with Durham's 
    water putty powder added to greatly reduce the water content, 
    which in turn greatly reduces shrinkage.  Two applications are 
    typically needed.  Allow at least one day cure time before 
    applying any coating over it.  Be sure to use the CLEAR 
    caulk to minimize its capacity to absorb moisture during its 
    service life.

    A less elastic filler is epoxy with Durham's water putty powder
    added.  Though lacking in elasticity, this filler does have the 
    advantage of absorbing virtually no moisture even under extreme 
    conditions.  This means that it won't release excessive 
    moisture during periods of rapid moisture evaporation through
    the paint film, such as when a hot afternoon sun heats up a 
    dark colored topcoat.  If that dark colored topcoat has much of
    a sheen, it could blister where excessive moisture tries to
    quickly escape.  However, epoxy fillers are very time consuming
    and fussy to work with.  I gave that method a thorough test
    on three occasions, and finally said "never again" except in
    such case as noted above.
  
    Sometimes siding boards are so dense and the nail heads so
    large that setting is impractical if not impossible.  In 
    those cases the nail heads will need a very heavy spot priming 
    with red iron oxide rust primer prior to applying the wood 
    primer.  They will also need a very careful finger-wipe 
    caulking after the wood primer is applied, or else water will 
    surely enter the surface here and cause premature  paint 
    failure.


7. Hand sanding

    60 grit floor sanding paper works well for all exterior hand
    sanding tasks.  Not only is it very long lasting, but it is 
    stiff and thus works very well on corners and narrow
    surfaces.  It can also be formed into a stiff rolled 
    shape for doing tight concave surfaces.

    For a little more money, you can avoid getting slivers
    (no small issue) by using sponge sanding blocks.  They are
    also long lasting and come in coarse, medium and fine grit.

    If you were gentle with the scraper and let the heat do
    most of the work as you heat stripped, and if you carefully
    scraped off all the residue as you went along, then a good 
    stiff hand sanding will complete the stripping task.
    
    Of particular importance is the rounding off of the 
    underside of each siding board, as well as the edges of 
    all trim boards.

    Blow dust off the wood and out of nail holes with a reversed 
    vacuum or leaf blower before priming.

Part II

The Coatings
    Outline:

      *  A conditioning soaking coat.
      *  Caulking and filling.
      *  A primer to complete the moisture seal.
      *  Finish coats primarily for sunlight protection.

      *  Encapsulation


    Overview:

    Start with a thin product with good sealing properties,
    heavily applied in the shade.  Follow with another coat 
    with good sealing properties to make sure the wood always 
    stays relatively isolated from outside moisture.  Finish 
    with a topcoat with good permeability (good breather).  
    The topcoat is mostly for sunlight protection.



8. The Soaker Coat

    I use only a clear acrylic bonding primer as my initial
    wood conditioner/sealer, but will begin by (reluctantly)
    including here a discussion of oil based primers for
    the benefit of anyone who still doesn't trust acrylic
    primers.

    Oil based primer:

    You get only one chance to penetrate the wood with a
    soaker coat of primer.  Once your initial prime is
    dry, no other coating will penetrate the wood.  The
    key when using oil base is to use a very thin product 
    and apply it very heavily.  You should also consider 
    applying it "wet on wet" for the deepest penetration.  
    This means recoating a section just as soon as that 
    section has mostly soaked in but not yet dried.  You 
    should not apply the soaker coat in direct sunlight.

    Here's a good choice for an oil base penetrating coat:
  
        Mix three parts alkyd primer to two parts mineral
        spirits.  (I recommend adding only a little or no 
        Penetrol, as it may interfere with the adhesion of 
        the subsequent latex coating.)  Flood it onto the 
        surface with a 3" wall brush.   Or mix it even 
        thinner and apply it "wet on wet" for the ultimate 
        soak.  There should be runs.  They won't have
        enough body to be detectable after the primer is
        dry.  Since mineral spirits is a light oil, it will
        increase the oil content of the primer.  Allow at
        least two warm dry days before applying acrylic
        primer over this soaker coat.

    If your wood is dried out, it would benefit from a 
    flood coat of Penetrol prior to oil based priming.
    Only an oil based primer should be applied over
    the Penetrol.  And in this case, allow a few days of 
    drying time before applying a latex primer or topcoat.

    Acrylic bonding primer:

    Pittsburg Paints Permanizer Plus is excellent for use as an 
    initial wood primer.  It has good penetration, and has the 
    additional property of being able to stabilize old dry cracked 
    wood.  It does this by sending its three dimensionally elastic 
    molecules into the pores of the wood and by winding its way 
    through every crack in the wood, forming a continuous elastic 
    barrier against water.  This primer has created success where 
    oil based primers have failed.  The difference is dramatic.

    Its urethane content also makes it surprisingly effective
    against tanin bleeding from cedar.  

    When using an all acrylic priming system on new or completely
    stripped wood, always start with Permanizer Plus (or with
    a variation described a few paragraphs down) and be 
    absolutely certain to flood it onto the surface, and only in 
    the shade.  Remember, you get only one chance to soak the 
    wood properly.

    Do not use Peel Stop as an initial wood primer.  My testing 
    in the summer of 1999 showed that Permanizer Plus quickly 
    penetrated the surface of dry gray wood and stained it to 
    a rich brown, while Peel Stop from Zinsser did neither.
    
    Speaking of dry gray wood - this is surface rot.  Sand it 
    away if practical, since the wood fibers are very weak 
    when gray and can fail, taking the paint off with it
    of course.  A good penetrater such as Permanizer Plus or
    Penetrol (if using an oil base priming system) is often 
    sufficient to overcome this surface rot if it is not extreme.

    If you ever need a cold weather (sub 50) version of
    Permanizer Plus, try this:

    1/2 gal XIM Peel Bond
    1/3 gal Sherwin Williams Clear Base Woodscapes (untinted)
    1/2 gal water
    (optional: Add 1 pint Penetrol (or Emulsa Bond))

    The Peel Bond provides the appropriate amount of
    acrylic resin.  The Clear Base Woodscapes provides
    the appropriate amount of urethane.  The Penetrol
    provides additional wood fiber conditioning.  The
    water provides better penetration.

    This blend makes a suitable replacement for Permanizer
    Plus at all temperatures between 35 and 90.  In fact, it
    has been my first choice regardless of temperature for 
    the past fifteen years, since it is much more readily 
    available.  There are few places that sell Permanizer
    Plus.

    For surfaces that are a complex mixture of bare wood 
    and existing paint, making spot priming impractical, 
    an alkyd primer is okay when the existing paint is alkyd 
    or oil base, but an acrylic primer such as the one just
    described should be used when the existing paint is latex.  
    It's always a risk to apply alkyd primer or alkyd paint 
    over latex paint.  The reasons for this are not chemical 
    incompatiblity but rather mechanical considerations:  You 
    don't want a coating which is a very poor breather over a 
    coating which is a good breather, as this can lead to 
    moisture buildup in the good breathing coat and ultimate 
    failure.  You also don't want a coating with little 
    elasticity over a coating of high elasticity, as this can 
    lead to alligatoring.

9.  Caulking and filling

    The caulking and nail hole filling is performed next, 
    allowing you to apply two film forming coats over it.

    My two favorite all-purpose caulks are DAP 35 year clear
    siliconized acrylic and White Lightning 40 year clear sili-
    conized acrylic. The DAP is lower water content, stiffer, 
    and can be painted over a little sooner.  Caulk every little 
    crack, tiny hole and end joint, however tight the joint may 
    be.    
    
    You should use a polyurethane caulk such as Vulkem, PL, or 
    Sherwin Williams for high movement "architectural joints",
    such as where fascia and crown moulding meet at outside
    corners.  Allow plenty of drying time.
    
    This is also the point at which filling the nail holes is
    performed.  See section 6 (sinking nails) above.

    Another excellent use for the DAP 35 year caulk is as window 
    glazing.  I resisted this method for years because I was 
    proud of my traditional glazing skills.  But caulk will 
    outlast glazing by dozens of years, will remove far more 
    easily should you need to replace a window pane, will save 
    an enormous amount of time right up front, and will have
    an acceptable appearance once you become proficient at 
    applying it.  It's been a frequent method of mine for many 
    years --  it depends on the particular project.  One often 
    needs to fuss with it using fingers or a flat razor after 
    application to make it tidy.  Be sure to prime the mullions 
    prior to caulking or glazing.  Also be sure to razor away
    existing paint from the window glass prior to priming and
    glazing.

10. Second coat - The Acrylic Primer
    
    After caulking you are ready for your second coat of
    primer, as the clear sealer alone is not adequate 
    moisture protection for the wood.

    You shouldn't use any alkyd products beyond the initial
    coat.  Any coating which forms a substantial film on the 
    surface needs to be elastic.   

    This is especially important whenever the wood has a high
    degree of unstability, such as in the case of old dry 
    cracked wood, plywood, poor cut wood, broad soft boards,
    or pine.  In fact in these cases, you should definitely 
    use an all acrylic priming and coating system, beginning 
    with the clear sealer described earlier.

    A pigmented acrylic primer such as 1-2-3 by Zinnser 
    works well over the penetrating coat.  This primer
    will provide pretty good film build and provide both 
    moisture protection and the beginning of sunlight 
    protection.  This coating needs to be applied heavily
    if it's going to do its work.  Be very careful to not 
    brush it beyond what is necessary -- it is more sensitive
    to overbrushing than other acrylic products.  Window sills 
    need an extra coat.

    If there is bleeding present after the clear sealer has 
    been applied, a coat of 1-2-3, or in extreme cases, multiple
    light coats of 1-2-3, would handle that as well.  Adding 
    yellow oxide to 1-2-3 makes it more effective against tannin 
    bleeding in cedar.  (The tinting base of 1-2-3 does not 
    provide good protection against tanin bleeding.)

    Another good option for the second coat of primer is a 1:1 
    blend of the clear sealer and the finish paint, the nature of 
    which I'll discuss next.  (Caution:  Do not mix 1-2-3 and
    Duration paint together.  You will get clay.)

11. Finish Coats

    Sherwin Williams exterior finish coats

    I use Sherwin Williams Duration Lifetime Coating exclusively.  
    The best Sherwin Williams paints have always had the best 
    ingredients in the optimum percentages.  

    Sherwin Williams Duration Lifetime Coating is a higher build,
    better bonding, more flexible coating than previous premium 
    acrylic coatings and is the ultimate finish coat for exterior 
    painting.  It even works okay as a bare wood primer in a pinch. 
    This product performs well down to 35 degrees.  I do not rely on 
    it for general bare wood priming, since most situations call for 
    better penetration, sealing or stabilization.  It can be used as 
    a two coat system over the clear sealer, but using 1-2-3 as the 
    next coat over the clear sealer will provide better moisture
    protection, as well as bleeding protection as mentioned above.

    I use eggshell finish latex for exteriors whenever I can,
    as opposed to flat, semigloss or even satin finish latex.  
    Eggshell finishes have just the right resin/pigment ratio to 
    allow the paint to both breath and shed water.  Ideally, the 
    topcoats should breath better than the primer(s) in order to 
    avoid moisture trapping.

    Eggshell finish latex paints also tend to have more ideal 
    elongation (elasticity) properties.     

    This means that I typically mix satin Duration 1:1 or 2:1
    with flat Duration to achieve an eggshell finish.  The 
    satin finish is particularly risky when using a dark
    color, as a hot afternoon sun can cause it to blister.
    It's unpredictable.

    There is a strong tendency for people to overbrush latex 
    coatings and to spread the coating too far.  One goal is 
    to apply a film of protection on the surface, not to 
    just color the surface.  Another goal is to transfer the 
    acrylic substance from the can to the surface in a 
    uniform film with as little disturbance of the resin as 
    possible - this is what insures long term film service.

    There should be a minimum of three coats of film forming
    product everywhere (except well shaded soffits).  This 
    might take the form of a clear sealer followed by two coats 
    of Duration, or a clear sealer followed by 1-2-3 acrylic 
    primer, then Duration.
    
    Anything less does not adequately seal the surface.  
    When moisture penetrates into the wood often, the surface
    wood fibers lose their integrity and the film fails at
    the wood surface, ultimately as the result of hydrostatic
    pressure acting on what has become a poor bond.

    A four coat system is recommended:  the clear sealer,
    1-2-3, then two coats of Duration.  Adequately sealing 
    the surface is important even for short term success.

    Soffits require less protection.  For well shaded soffits 
    that have only a small percentage of bare wood exposed
    after scraping, you could actually get by with just a one 
    coat process: mix one part Penetrol or Emulsa Bond with 
    three parts acrylic finish coat.  This gives the coating 
    better sealing and surface wetting properties.  (Penetrol
    mixes with latex paint just as well as Emulsa Bond and
    provides the same long term performance.  I always have
    Penetrol in stock and therefore use it exclusively.)

    To review: I favor the all acrylic systems even when the 
    existing substrate is oil based.  I rely on the clear sealer
    as a whole house initial primer, over bare wood of course,
    but also over chalky paint and checked paint (if sound).  
    It binds any residual dirt on the surface that pressure 
    washing leaves behind and even helps rejuvinate the old
    paint film.

    
12. Encapsulation

    Encapsulation can be regarded as stabilizing a substrate,
    whether the substrate is bare wood or old paint.

    Problem boards

    Boards with horizontal hairline cracks as well as larger
    cracks need to have a high stretch caulk troweled into their 
    cracks.

    There can be over a hundred such areas on a house with these
    types of lumber problems, and replacing all such boards can
    be cost prohibitive, especially when dealing with fascia 
    boards and crown molding, the very boards that most frequently
    have long running cracks.

    Old checked paint

    (This section is highly optional.  It examines the concept
    of layering coatings for optimal encapsulation.)

    First of all, one needs to learn to recognize the difference
    between stable and unstable old paint.  Generally speaking,
    if the paint is not seperating from the substrate or even
    hinting at it, then the paint is stable, even if heavily
    checked.

    But checked paint can become unstable if not encapsulated
    correctly:

    It's desirable to use a very elastic final coat over the 
    checked paint, or else the checking will transmit through
    it in time.

    Unfortunately, a coating which is sufficiently elastic to
    accomplish that might also pull the old coating loose from 
    the substrate through repeated expansion and contraction 
    with temperature changes.

    Applying an oil based primer over the checked paint 
    prior to an elastic coating will not solve the problem, 
    because the elastic coating will still do work on the checked 
    paint by virtue of transmitting its force very effectively 
    through the relatively inelastic coat of new oil primer.

    What to do?  The secret is in using a go between coating
    that is not elastic enough to flex the checked paint loose,
    but elastic enough to force the elastic topcoat to do much
    of its work on the go between coating.  The flex force of
    the elastic topcoat is largely dissipated in the go-between
    coating.
  
    I find the definition of the paint film attribute "elongation"
    to be misleading:  A paint film with an elongation factor
    of 1 means it will stretch to 2 times its own length before
    tearing.  An elongation factor of 2 means it will stretch to
    3 times its original length before tearing.  So I use a term
    called "stretch factor" to distinguish it from the industry 
    defined term - "elongation", even though it's the exact same 
    concept.

    A coating with a stretch factor of 1 means that the coating 
    will tear upon trying to stretch it beyond its original length 
    of 1 unit.  A coating with a stretch factor of 2 means it will
    tear when stretched to double its original length.
  
    Here are some examples among quality exterior coatings:
    Sherwin Williams Superpaint flat      1.3
    Benjamin Moore Moorlife flat          1.5
    Benjamin Moore Moorgard eggshell      1.5 
    Zinsser 1-2-3 acrylic primer          1.6
    Sherwin Williams Superpaint satin     2.1
    Sherwin Williams Duration flat        2.5
    Sherwin Williams Duration satin       3.1
    These numbers are approximate values, based on averaging
    my test samples using white or light colors.

    I've had great success in longterm encapsulation using
    paint or primer with a stretch factor of between 1.3 and
    1.6 as my buffer coat, but prefer the low end of this range.  
    It must be applied heavily or in two coats (1.3, then 1.6)
    to be most effective.  Start with a light coat of the clear
    sealer, especially if there is any bare wood mingled with the 
    checked paint.  It's function is to seal the wood and bind 
    any dust on the surface.  It's thin film will not play a role 
    in the stability of the checked paint one way or the other.  
    (It has a stretch factor of 1.5.)
  
    Duration is of course my choice for the final coat over
    the buffer coat(s).

    I've yet to see failure upon returning to inspect old job 
    sites where this method was used.

    There are also (dubious) heavy bodied encapsulation coatings 
    available.  Take a look at their elongation properties before 
    committing to their use.



13. Overpainting

When paint separates from the substrate, there is always 
hydrostatic pressure involved.  This is the pressure of
water evaporation.  To reduce the possibility of this occuring,
you must use coatings with a favorable ratio of adhesion to
permeability, you must apply them in the correct order, and
you must not overcoat a surface.  

A heavy build up of coatings over the years can work against
you in two ways:

When the permeability of the overall coating system reaches 
a certain low point, the film will separate at the weakest link, 
usually at the surface of the wood, especially if the initial 
primer did not penetrate deeply enough into the wood or did not 
enhance the wood fibers.

Also, as the total thickness increases, the elasticity decreases,
leading to cracks in the film.

Which is the biggest problem is hard to say.

To review what was said earlier about primers and topcoats:

Start with a product with good sealing properties, heavily 
applied in the shade.  Follow with another coat with
good sealing properties to make sure the wood always stays
relatively isolated from outside moisture.  Finish with a
topcoat with good permeability (good breather).  The topcoat
finalizes the moisture protection and provides sunlight 
protection.

When encapsulating old paint, there is risk of creating 
hydrostatic pressure beyond what the old coating can resist, 
but that can sometimes be a good risk management decision, 
considering the cost of paint removal.

Note:

On some projects, I've removed and reinstalled all 
the siding back side out, running each piece through 
a table saw to remove the paint from the bottom edge.  
I hand sand or power sand the face to freshen it.  The 
total time required is about the same as for stripping 
with the triple heat gun as described above.  If you are 
handy with a flat pry bar, you can remove all the siding 
with no damage.  It's important to grind down your flat 
pry bar until it is very sharp and has a very slim profile 
over the first couple of inches.

Reversing the siding works only if your house has 
vertical corner boards, or if you are willing to 
install corner boards.  Otherwise the bevels at the 
corners will be backwards.  I once converted a house
to vertical corner boards and it went very smoothly.

Mark the locations of each siding board on the adjacent
window frame or corner board prior to removal.  Scrape 
the edge of the window frame or corner board clean of 
paint so that you can pry off the siding boards without 
binding.

Work from the top down.  Use a specialty pry bar to
extract the nails from the top two or three siding
boards.  It is smooth sailing the rest of the way.















end painting document                                   rogcad.com  site map
===========================================









Special Relativity explained in absolute terms -

eliminates the twin paradox, shows Einstein's clock sychronization
diagrammed in absolute terms, and ends all confusion regarding
relative frames of reference.  Completely compatible with, and in
fact subsumes, Einstein's relativity.  Not Lorentzian relativity.
Reveals what is transpiring behind the scenes of Einstein's
treatment.


Documents:


Relativity in Absolute Terms.
My most comprehensive online document.  A concise overview
of why special relativity must be diagrammed in absolute terms.


Twin Paradox Animation.
Expanded text, and animation of the twin paradox.  (Embedded youtube animation.)


Twin Paradox Explained.
A similar discussion of the failure of spacetime diagrams.  


Twin Paradox Animation.
Alternative text, and animation of the twin paradox.  (Embedded youtube animation.)


Absolute Frame of Reference
Absolute frame of reference in the physics community.


Free pdf file of the book:

Relativity Trail, free pdf format, with 192 pages, 65 diagrams 
and 75 illustrations, will provide you with complete 
detailed algebraic derivations of all the 
kinematical effects of special relativity.  
Everything is charted out in absolute terms against 
the rest state of the universe for perfect clarity
as well as soundness of theoretical basis.  It is 
the totality of the universe that imparts the 
inertial properties of clock rates and lengths
which generate the effects of relativity.  This 
is explained in detail in Relativity Trail.


Excerpts from the book Relativity Trail with included images.


Einstein explained in excerpts from Relativity Trail.


Diagrams and derivations from the book Relativity Trail.


---------------------------------------------------------------


Chaos etc - equations and graphical output.
Eight equations generating exotic behavior,
along with the program code and graphical output.



RogCAD - 3D CAD software for Windows and DOS -

featuring keyboard entry of points, lines, planes, cubic
elements and curved elements.  Your design elements are
guaranteed to fit together seamlessly.  Text file data
allows for easy and robust editing of design elements.
There is automatic surface modeling with light source
direction, and an advanced customizable color palette.



RogCAD Girder and Panel Building Set
3D CAD virtual building set, modeled after the 
1957 - 1962 Kenner Girder and Panel building set.


---------------------------------------------------------------

Jester
His story and music videos


The Hermit Thrush
Streaming three minute audio of the Hermit Thrush


Uncle Remus illustrations by A. B. Frost
with a note from author Joel Chandler Harris

---------------------------------------------------------------

rogers-antique-restoration.com
Antiques and furniture restoration service

Vintage American Locks
Vintage and modern day padlocks from
John Junkunc's beloved American Lock Company

---------------------------------------------------------------

home page:   rogerluebeck.com