Stripping paint from wood
When you come to repaint a surface, you will be wasting your time
if the surface is not properly prepared. Providing that the previous
paint surface is sound, all you need do is just rub it down with a
medium sandpaper, dust off and the surface is ready for its first
However, there are situations where the previous coats of paint
need to be stripped off:
If the paint is damaged, peeling, pitted, badly chipped or crazed,
repainting will not achieve a satisfactory or long-lasting finish.
Where you want to go for a 'natural' wood grain finish.
A heavy build-up of paint on the closing edges of doors and windows
may be causing it to stick and another coat of paint will just make
The more coats applied to carved architrave or other mouldings can
cause the original carving to become 'dulled' or disappear completely.
There are three basic ways of stripping paint from timber: by mechanical,
heat and chemicals. Each has its own advantages and disadvantages
- sometimes a mixture of methods may be appropriate.
WARNING: In older properties, the paint may contain lead (in the
UK, earlier than about the late 1960's). Added care must be taken
if there is a chance that you are stripping lead based paint - avoid
mechanical and heat methods of stripping (these could produce lead
dust or fumes) and wear an appropriate breathing mask. Seek guidance
to ensure the health of you and your family is not effected.
Whatever method you are going to use, it is always worth while
trying it out on a 'hidden' area first to make sure it works.
This method is only suitable for complete stripping where a very
thin coat of paint has to be removed.
Start by using coarse sandpaper and as the grain begins to appear
change to medium grade. On flat surfaces, wrap the sandpaper around
a wood or cork block. Even with a thin coat of paint you will need
plenty of effort.
To reduce the amount of dust produced, you can use wet and dry
sandpaper with a wetting of water, but avoid this if you are intending
to varnish the wood to show natural grain, the dust paste will be
absorbed by the grain and its removal will require a lot more dry
sanding. When wet sanding is undertaken, ensure the wood is allowed
to fully dry out before the final dry sanding and painting.
Hand sanding is not really satisfactory for carved or shaped timber
as the action of sanding will tend to flatten the detail no matter
how careful the sanding is undertaken.
There are various sanding attachments available for power tools.
Circular sanding discs mounted in an electric drill are not easy
to work with and there is a high risk of scoring the wood. If the
wood is damaged in this way, you will have to do a great deal of
repair work before you can repaint it. Careful use of a disc to
remove the initial layers of paint can make the job easier but don't
expose the wood grain with a disc.
A Sanding Drum is a fast and effective method of stripping paint.
The drum comprises a foam drum with an abrasive belt fixed to it.
The belt should be used along the grain to avoid any scuff across
the grain of the wood. The drum sander is quick and efficient, but
has the drawback of producing large amounts of dust. Also, as it
only move in a single, linear direction, there is a risk of score
marks on the surface.
Sanding drums are available with various grades of abrasive (coarse
to fine) - use the appropriate grade for the stage of sanding. Start
with a coarse grade and change to a fine grade as the grain becomes
exposed. Do not use one grade, the job will either take longer than
necessary (if only a fine grade is used) or the finish will be disappointing
(if only a course/medium grade is used).
As with hand sanding, the sanding drum is not really satisfactory
for carved or shaped timber as it tends to flatten the detail.
The Orbital Sander power tool is 'more' gentle (and that also means
slower) than the Sanding Drum, again change the grade of abrasive
as you strip the paint, and again, it is only really suitable for
flat surfaces. Keep the sandpaper free of dust and keep the sander
moving, the small circular movements of the sandpaper can give a
very good finish to a flat surface.
Also available is as a power drill accessory is the paint and varnish
remover (a metal disc with perforations punched through - sort of
like a cheese grater). This is suitable for removing the top layers
of thick paint but must not be used once the wood grain is exposed
as the grain will be damaged.
Always try to take workpieces out-of-doors when hand or power tool
sanding, this will reduce the mess and the improved ventilation
will keep dust problems to a minimum. Remember that any air borne
dust will travel from room to room within a house, and, if working
indoors, you will be unlikely to restrict dust to just one room.
For personal safety, always use a dust mask and eye protection
- this applies to everyone in the immediate area, not just the person
doing the sanding.
Today both blowtorches and heatguns are available to strip paint,
the former using a naked flame to heat the paint while the latter
uses just heated air. Whichever tool you use to heat the paint,
you will need a number of scrapers to remove the paint, various
types are available, straight edge, convex, concave, pointed to
suit the timber profile being stripped.
With a blowtorch, the flame can be adjusted to give various sizes
and temperature of flame, heatguns usually have one or two temperature
settings, and the size/shape of the airflow can be adjusted normally
by fitting different nozzles. Before beginning stripping paint with
either tool, it is worthwhile getting the feel of the blowtorch/heatgun
by practising on a piece of scrap painted wood. Hold the tool at
a constant distance, (generally about 150-200mm (6-8in) from the
paintwork). Move the tool back and forth across a small area and
the paint should start to wrinkle and then bubble, it is then ready
to be scraped off. If the paint sticks to the adjacent paint rather
than easily lifts off, play the flame/hot air over the area again
and scrap again.
There is always a risk that the flame or hot air will scorch the
wood by being concentrated on a small area for too long, keep the
tool moving so that it is the paint which gets hot rather than the
underlying timber. Be very careful when using heat to strip paint
new glass (such as in a window frame), if too much heat is applied
to the glass, it can easily crack.
Application of heat will never produce a stripped surface which
can be painted straight away, you will always need to sand the exposed
timber to get a satisfactory surface. Heat can cause the release
of resins from the underlying timber and also for any filler in
the timber to become detached.
Remember that the flame or hot air can cause damage around the
area of application, keep away from plastics (such as guttering)
and fabrics (such as carpets and curtains). Wear a pair of heavy-duty
gloves and protective goggles.
You will always need to sand the stripped timber before painting,
use coarse/medium/fine sandpaper as necessary.
Most areas of UK have companies specialising in stripping complete
items by dipping them in a tank of chemical solution, while obviously
not practical for skirting boards or other timber fixed to the structure
of a building, these facilities can be ideal for pieces of furniture
or doors. However, be warned, sometimes the glue used in old furniture
will not stand upto the process and you could end up with a 'self
assembly' kit of pieces without instructions !!
Chemical stripper available for DIY use can be fairly expensive,
so their use may need to be restricted to moulding and shapes where
their use is unsurpassed. Chemical strippers work best on thin coats
of paint where one application can remove the paint back to bare
wood. Thicker coatings may require two or three applications.
Two forms of chemical strippers are widely available, a gel type
liquid which is applied by brush and a paste type which is laid
over the paint to work its wonder. Whichever type is used, remember
that it is a form of corrosive, so if you cannot take the piece
of work out of doors, protect the surround decoration to avoid accidental
splashes and drips.
Gel type is normally applied using a brush, usually requiring an
initial thin coating to start the process, then followed by a generous
application. After a minute or two, the paint surface will start
to shrivel and it can then be removed using a paint scraper. As
the stripped paint is rather sticky, wipe the scraper on old rags
or newspapers to keep the scraper as clean as possible. Use the
appropriate scrapper for the surface being stripped (i.e. straight,
convex, concave or pointed).
Keep the scraper as upright as possible to avoid it digging into
the wood and damaging the surface.
After the first application of stripper has been scrapped off,
inspect the workpiece, if large areas of paint are still in place,
repeat the process with another application of chemical. Be aware
that some types of paint may not be affected by the chemicals in
a particular brand of stripper - in this case you may consider using
an alternative brand or mechanically removing it.
The paste type of stripper is available 'ready for use' or as a
powder requiring the addition of water. Whichever type is used,
when the paste is ready for use, apply it to the painted surface
using a putty knife, take special care to ensure that it is applied
right into the bottom of any carving or other recesses. You cannot
see the chemical reaction taking place, so you have to be patient
and wait the specified time before pulling the paste away - try
a small area to begin with just to check what has happened, the
coats of paint should come away with the paste.
No matter how careful you are when using chemicals, there will
always be small pieces of paint left on the surface, some may be
so small that they are not obvious to the eye. As a final stage,
apply a thin layer of stripper to the surface and carefully rub
over using medium or fine wire wool. Only use small pieces of the
wool at any one time and keep turning/replacing it so that a clean
area is always presented to the surface.
A surface stripped with chemicals needs to be neutralised before
applying fresh paint. So, using a constant supply of clean rags,
thoroughly wipe down the surface with white spirit or the appropriate
solvent recommended by the manufacturer of the chemicals. Where
the manufacturer recommends water to neutralise the stripper, this
often indicates a 'less harsh' stripper and the use of water can
raise the grain of the wood requiring addition sanding before painting
can be undertaken.
Whenever possible, always start and finish the stripping in the
same day and don't let the surface dry out - the chemicals will
penetrate the surface of the wood and if it dries into the grain,
it will become harder to remove/neutralise.
The stripping chemicals may affect some fillers used in the underlying
wood, so these may need to be replaced before painting can commence.
The chemicals and fumes may be harmful so always follow the manufacturers
recommended safety precautions - normally these include only working
in well ventilated areas, wearing gloves and goggles.