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HOW TO: Use varnishes, woodstains and dyes
Introduction
This 'How to' describes how to achieve the best possible finish for your
wooden surfaces. It shows how to prepare surfaces, how to colour them
using wood dyes and stains, and how to apply different types of varnish.
There are two key things to remember. The first is that good preparation is
essential. Before you apply any finish, make sure that your wood is dry, clean,
well sanded, and free from wax and grease.
The second thing to remember is that moisture will undo all your good work. To
keep water out of your wood, you will need to apply finish to every surface with
special attention paid to ends. If you're working on an exterior door or window,
seal any gaps between wood and masonry after you've applied the finish.
What you ll need
Materials Tools & equipment
See the Buying Guides for varnish, woodstain Abrasive paper
Scrapers
and dye for advice on choosing from the wide
Bucket and sponge
Varnish and woodstain brushes
range of wood finishes available.
Cellulose thinner
White spirit
Clean lint-free rag
Wire wool 00 grade
Cork sanding block
Wood filler
Filling knife
Hint
Never use interior varnish in outdoor or exposed situations.
Safety first
" Be sure to follow the manufacturer's instructions for preparing and
applying finishing products.
" Most varnishes and stains are flammable and toxic. Take the following precautions:
Keep away from sources of ignition
Don't smoke
Avoid contact with eyes
Keep out of reach of children
Used rags may self-ignite so keep outdoors in a metal container
Wear rubber gloves or a good barrier cream.
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HOW TO: Use varnishes, woodstains and dyes
Preparing new wood
1. Clean the surface
Dust, grease and wax will prevent wood stains and dyes penetrating, or varnishes
adhering. Certain stains will need to be wiped over with white spirit or cellulose
thinner before and after sanding.
2. Sand the wood
The key to success is a series of sanding stages. Work by hand or use a power sander.
Always sand in the direction of the grain, using a progressively finer abrasive paper (fig. 1).
fig. 1
Round off all sharp edges, especially on exterior timber as this is where your finish is
most likely to break down.
3. Apply preservative
Apply two coats of clear preservative to all exterior timber. Interior woodwork that's
built in or fixed will need one coat. There's no need to apply preservative to free-
standing domestic furniture.
Preparing wood that's already varnished
Do you need to strip the old varnish?
Before trying to recoat old varnish, test a small piece. If your new varnish causes the
old varnish to lift or wrinkle, it's best to strip the old varnish completely and start from
scratch (fig. 2). If the surface remains sound, you can simply recoat.
Stripping old varnish
Be sure to use the correct stripper. Some paint strippers won't remove varnish, and
you'll need a 'hard varnish' or 'cellulose finish' stripper for some interior
fig. 2
sprayed varnishes.
Wash off all traces of stripper. Fill cracks, holes and open joints, colour-matching your
filler to the timber (fig. 3). If the stripper has bleached any areas, stain them to match
the original colour. Sand the surface carefully and remove all dust before varnishing.
Hint
To remove all dust, use your vacuum cleaner fitted with a brush or narrow
nozzle (fig. 4).
Recoating old varnish
If the old varnish is sound, just clean the surface with water and detergent. Fill
any gaps, colour-matching your filler to the varnished surface. Rub smooth with fine
'wet or dry' paper.
Make sure that the wood is dry before you revarnish. Moisture can prevent good
adhesion and cause a milky appearance. Wait for dry weather before varnishing
exterior surfaces.
fig. 3
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HOW TO: Use varnishes, woodstains and dyes
Applying preservative
Apply wood preservative only to bare, clean timber:
" New wood
" Wooden surfaces that have been completely stripped and cleaned, for
example, window frames, exterior doors
" Previously preserved timbers, for example, constructional, garden timbers.
Brush liberally onto all surfaces of the timber until the wood is saturated. Pay
special attention to end grain.
Exterior new wood and stripped wooden surfaces will need two coats of preserva-
tive. Interior new wood and timber that's been preserved before needs one coat.
Allow 24 hours drying time between coats, and wait 3 5 days before applying
fig. 4
any other finish.
Colouring wood
Order of work
Dye, stain or varnish the sections of a panelled door in this order (fig. 5).
Coloured polyurethane varnish
You can mix different colours of polyurethane varnish to get the shade
you want.
Thin the first coat: 10 parts varnish to 1 part white spirit. Brush on to
exterior or interior wood. Apply a second unthinned coat, then further
coats until you have the finish you want.
fig. 5
Sand lightly between coats, using fine abrasive paper. Allow 6 hours drying
time between coats.
Coloured varnish may produce an uneven coat on your timber. Apply a sealing
coat of clear thinned varnish first. Allow to dry and sand lightly. Then apply
further coats of the coloured varnish until your surface is the colour you want.
Wood dye
Before using a wood dye, test its effect and depth of colour on your
particular wood (exterior or interior). Dye an inconspicuous area on your surface,
or an offcut of the same timber.
Use a folded lint-free cloth rather than a brush to apply the dye. Keep all working
edges 'wet' to avoid a patchy or uneven surface. Wear plastic gloves to protect
your hands.
When dry, rub (burnish) the surface with a dry, clean, lint-free cloth. This will remove
any surplus dye and leave an even surface. Don t sand, even lightly at this stage, as
sanding tends to produce a streaky appearance.
The first very light sanding should be after the first diluted coat of varnish is fully
dry. Slightly heavier sanding can be done after the second undiluted coat of varnish
is fully dry.
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HOW TO: Use varnishes, woodstains and dyes
Colouring wood (cont.)
See manufacturer's instructions for drying times, and don t mix dyes from
different manufacturers.
Stripped timber
You may find that the surface of stripped timber becomes rather patchy after it's dyed.
This problem is caused by old finish that's left in the grain.
It s often better, therefore, to use coloured varnish to change the colour of stripped
timber. Use clear varnish for the first coat, followed by the number of coats required,
rubbing down between each coat.
Woodstain
Don t:
" Stir or thin wood stains before using
" Use over varnish, paint or linseed oil putty
" Apply in temperatures below 5°C
For best results use a varnish and woodstain brush, made especially for use with wood
care products. Brush on evenly, avoiding over-spreading.
Coat all surfaces to provide total protection. Pay special attention to the treatment of
tops and bottoms of doors, undersides of sills, sashes and end grain.
The original colour and porosity of your wood will influence the final colour of your
surface after staining.
Previously stained wood needs one coat and bare wood need two coats. Allow 16 24
hours drying time.
Previously stained wood
On previously stained wood, treat bare or bleached areas with wood dye and allow to
dry. Touch in these areas with exterior wood stain and allow to dry. Lightly rub down
before applying a complete top coat.
Refinishing woodstains
Woodstains deteriorate over a period of 2 4 years, depending on the severity of the
weather, and they can become very dirty.
To refinish your surface, first wash it down, ensuring you remove all grease. Allow
the surface to dry and apply a coat of woodstain. If a second coat is needed, sand
first coat lightly and dust off.
Applying clear varnish
Yacht varnish
Yacht varnish is generally used for exterior wood. Brush on, using the best brush you
can afford, and rub down lightly between coats. Thin the first coat: 5 parts varnish
to 1 part white spirit. Apply 3 4 further unthinned coats allowing varnish to dry
thoroughly between coats.
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HOW TO: Use varnishes, woodstains and dyes
Applying clear varnish (cont.)
Take care to treat the timber all round, especially the end grain. This prevents water
penetrating behind the varnished surface.
Clear polyurethane varnish
Polyurethane varnish can be used inside and out.
Thin the first coat: 10 parts varnish to 1 part white spirit and brush on. When dry,
rub down with fine abrasive paper, then apply a second unthinned coat. Apply further
coats until you have the finish you want. Allow 6 hours drying time between coats.
Acrylic varnish
Apply liberally across the grain with a clean brush. To finish off, draw the brush lightly
in the direction of the grain. Allow three coats for maximum durability.
The water content of the varnish may cause the first coat to raise the grain. If this
happens, lightly sand the surface. You can use fine glass or garnet paper, but fine
'wet or dry' paper and water is best. Wash the sanded surface with clean water.
Apply acrylic varnish to interior and exterior wood and to floors. Bare wood may
be stained before varnishing.
Cleaning brushes
If you've used:
" Wood dye
clean with white spirit or methylated spirit
" Woodstain
clean with white spirit or cellulose thinner
" Preservative, yacht varnish, polyurethane varnish
clean with white spirit
" Acrylic varnish
clean with water if the brush has hardened, soften with cellulose thinner.
After cleaning with solvent, wash all brushes with detergent and warm water, rinse
HB
thoroughly in cold water, and dry carefully.
Homebase.co.uk 5
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