I know you wouldnt think so from the absolutely dreadful weather we’ve been having for the past FIVE MONTHS!!! but Spring is actually JUST AROUND THE CORNER!. No sooner will you know it but the gardens will be blooming, the birds singing and young painters’ thoughts turning to EXTERIOR PAINTING. So put your Parka, gloves, hat and scarf on and take a look around the outside of your house. Look for the ravages of this terrible and lonnnnggggg! winter we’ve had. Paint flaking? Rotten wood? Tiles slipped? Gutters broken? Give us a call now as we are already filling up our schedules for APRIL, MAY, JUNE and JULY. Have faith–we will get some decent weather soon.
Preparation of surfaces
Article number two. Second in a series of articles on preparation for Exterior painting.
Scraping off is the process of removing defective paint and other coatings from a surface which is to be repainted.
How much scraping off is needed depends entirely upon the conditi0n of the surface to be repainted. All loose and flaking paint is to be removed from wood, masonry and metal surfaces before any further preparation can take place.
Loose and flaking paint can be scraped off wood using a stiff-bladed scraping knife. A shave hook for crevices and/or a wire brush can also be used for this purpose. One can have a selection of different size scraping knives and wire brushes to deal with different profiles in the wooden surface.
Again one can use scraping knives, wire brushes and shave hooks for crevices. The object is to remove ALL loose and flaking paint from the masonry surface.
Caution should be used when using a wire brush on masonry surfaces. One can easily start removing perfectly sound paint from the render, brick or stonework and this is unnecessary and simply creates more work than is needed. Sound paint–i.e., paint that is adhered well to the surface, not cracking, crazing or showing other signs of defect, need not be removed prior to repainting. ( unless of course it has been specified to strip off all paint)
Normal metal surfaces encountered in exterior decorating are iron railings, gates, balustrades, staircases and rainwater and soil pipes and gutters.
One will normally use a wire brush and scraping knife to remove loose paint from metal surfaces. Another method is ‘tapping off’ and this involves the use of a small ball-peen hammer to ‘tap’ the loose or old paint surface. The paint is thus broken up and it is then scraped off with a scraping knife or wire brush. This is actually used in conjunction with or as an alternative method to ‘burning off’ when one is attempting to remove all or most of the old paint from a metal surface–though it can be used–with care–to effect removal of loose and flaking paint only.
A common problem with iron railings and other iron items is rust–or oxidisation. This is a natural chemical reaction of iron with oxygen. Rust erodes iron. All eroded and rusted iron must be scraped off prior to painting. After scraping and wire brushing off the loose rust one treats the rust affected areas with lead tetroxide ( red lead ) primer or some other proprietary rust primer. This seals the rust-affected areas from any further exposure to oxygen and thus halts the rusting process. Sometimes two coats of such a rust primer may be needed prior to painting.
This word simply means, in the context used here, ‘ the surface below the paint’
So with a painted wooden window the substrate will be wood, with a rendered wall the substrate is the sand and cement render, and with a cast iron railing the substrate is the iron itself.
More on substrates later.
The following series of blogs will deal with the different important elements of exterior painting. The first series will concern Preparation, to be followed by Base-coating then Top-coating.
Preparation of surfaces. article 1.
Someone once said that when planning any event or performance–the maxim is –8O% preparation, 20% event!!
This principle applies equally well to exterior decorating.
Preparation of exterior surfaces for painting is at least fifty percent of any exterior painting job.
What are the stages of preparation for exterior painting?
This applies anywhere in the country but especially so in large cities such as London. Masonry and wood surfaces become ingrained with carbon, soot, dust, soil and all the other pollutants that are part of the everyday atmosphere of a busy city. Surfaces must be cleaned of these before any exterior painting is commenced. Paint will not adhere to surfaces which are soiled, greasy or carbonised.
The amatuer decorator–or the negligent or untrained one–will not give this step the importance it deserves. And unfortunately this omission will not always become apparent until a few weeks or months after the painting is ‘finished’. This is because it is not possible to detect ‘uncleaned’ surfaces once the paint has been applied. The surface looks freshly painted–and it is–but the probability is that the paint finish will not last anything like as long as it would had the surface been properly and thoroughly washed down.
There are two main methods for washing down.
1. High Pressure water.
If the access permits it, and one has a power and water supply available, power washing can be an efficient and effective method of cleaning exterior surfaces. One must take care with the angle of the jet not to dislodge mortar joints or to spray the water jet through cracks or gaps in windows and one does not apply this method near to electrical fittings, lights, cables etc.
2. Bucket and sponge.
The traditional method of bucket and sponge is perfectly satisfactory. One uses a small amount of detergent in the water to help with cutting through carbon and grease deposits. If you have to increase the detergent it is important to rinse with a second bucket of clean water to remove detergent residue. Again, take care with electrical fittings, and not to cause water damage to internal surfaces or furnishings.
Use a crevice brush to access awkward places.
Clean off all soil, dust, carbon and grease. This action alone will often greatly improve the appearance of external surfaces–and it will leave the masonry, brickwork and woodwork in a clean and grease-free condition ready for the next stage of preparation and subsequent painting.
I hope you find this useful. If you have any questions about preparation of exterior surfaces or about any other decorating topic please contact us. The next article will deal with repairs to masonry, brickwork and exterior wooden surfaces.