Painting Interior / Exterior Woodwork.
All good jobs, painting or otherwise start with preparation, with painting this is key.. ” Failing to Prepare you are Preparing to Fail ” Benjamin Franklin.
Many people whom complain about paint peeling off or report an issue, most will have failed to prepare the substrate correctly. Paint does not lift or peel for no reason and these days there really is no bad paint just bad painters. Paint is made generally in very large quantities and has to be checked for a number of things before being tinned and leaving the factory, all paint tinned off, the manufacturer will retain samples of the batch and draw downs that show opacity and drying characteristics. Should there be any complaint later these samples are referred to and they can cross check any issue, if there was 1 bad tin there will be hundreds as paint is made on an industrial scale thousands of litres at a time in some cases, as you may imagine it is not in the manufacturers interest to let a bad batch leave the facility.
Preparation.
Existing painted surface :
Give a light abrasion with a 220 -320 grit sanding pad, you are not trying to sand through to the bare wood below, merely putting light scratches in the surface for the new coating to have something to grip on to. Remove any loose flaking old paint, if you do break through to bare timber you may need to prime. If it is just a few small areas you can spot prime using a coat of the fresh paint, if there is a significant area we would recommend the use of the appropriate primer. Once this is complete give the whole surface a wipe down with a damp cloth or sponge to remove the sanding dust and pollutants and contaminants, externally these could road traffic film, mould spores, bird pooh. Internally greasy hand marks and other such things. Use a little warm soapy water or sugar soap.
New wooden surfaces :
We would suggest understanding the timber you are painting as different species require differing approaches. Soft wood external would require a preservative, hard wood species would not. Internally you would not need to preserve any timber.
Soft wood ( European Redwood – Pine )
We would suggest the use of a knotting solution on the knots, knots are where the branches once came out of the tree. Knots are classified as live or dead… Live knots more noticeable on exterior joinery can exhude resin, dead knots can leach a tanning through the paint leaving many small round yellow patches which are more visible with pastel or pale colours. The use of knotting prevents the tanning, in the case of external live knots, nothing will prevent the sticky resin exhuding.
Exotic species – Sapele, Iroko, Red Grandis, Meranti + More
These timbers particularly with water based paints may be troublesome, they are generally oiler species more suited for exterior use, with the oils come tannings which again can strike through the paint leaving yellow / brownish marks, again far more noticeable in pale colours.
You may wish to give the timber a light abrasion to remove burs and fibres the timber would also benefit from a wipe down with a lightly dampened cloth with Methylated spirit on, this would remove any milling glaze that maybe present.
Milling glaze occurs on newly machined timber, basically the mechanical process’s in joinery manufacture help the natural oils in the wood migrate to the surface, planning, sanding cause this. The milling glaze can prevent the paint from keying to the substrate, this will later cause the paint to delaminate.
Moisture content of wood is also important and should be around 12 – 20% too low and the timber particularly externally will expand too much and may cause the paint to fail, too much moisture and the wood may contract with similar results.
We would recommend exterior joinery be painted with a Microporous paint system, this acts similar to the Gortex™ clothing allowing moisture to wick through the layers of paint rather than being trapped behind the paint where the wood would then rot like the wooden windows of a few years ago.
All the prep completed it is time to paint …
Using a good quality paint brush or if you have large flat surfaces you can use the mini rollers, using a paint brush to get in to corners or to equal any runs you may get.
Water based paint first I would recommend wetting the brush, run the tap and allow the bristles to get wet and ring any excess water out, this helps the cleaning process at the end and primes the brush to start giving a smoother start to your painting.
Load the brush / roller with paint and generally follow the wood grain maintaining a wet edge, water based paint tends to dry a lot quicker than traditional solvent based paint. Drying quicker can mean you may receive tram lines … ( Brush marks ) you can prevent this by adding 5 – 10% of clean water to ease the flow, many trade professionals use Paint Conditioner ( Floetrol ) which extends the open time ( drying time ) slightly, this allows the paint to flow better leaving a professional finish.
Water Based or Water Bourne Paint
Generally water based coatings dry quicker, have little or no smell, much better for the environment, for our health, Do Not Yellow ( in the case of White ) allow you to get a job done in a day, Primer / Undercoat and 2 top coats. Application to many more substrates, some products do not require primer or undercoat, particularly the Bedec Multi Surface Paint range.
Solvent Based Paint
A more traditional paint, 16 – 24 hour drying between coats, potentially 3 days to do one job, several days of solvent smell around the home, cleaning brushes in white spirit. Coating will not necessarily last any longer.
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