In the last five years there has been a huge shift in the painting and decorating industry regarding oil-based and water-based wood paints. This is due, mainly to new EU regulations on volatile organic compounds (VOC’s).
What does this actually mean though?
We were working in Stirling last week and a customer asked me what the difference is between the two types of paint. This is by no means the first time I have been asked this question, it tends to come up, a lot… so I thought it was time to write an article so non-professionals can make a more informed choice about what paint to buy and why…
Like many other professionals and DIYers alike, we have used oil-based paint products on woodwork for years. However, such products (you know the ones, they stink to high heaven and take ages to dry) are really bad for the environment and not great on your health, so many decorators, ours included, have been looking for decent, quality, alternatives.
For this reason we have seen a dramatic rise in water-based products appearing on the shelves of DIY stores and decorator centres such as Dulux, Johnstones and Crown. This is because water-based paint products have very low levels of VOC content compared to oil-based paints so they are becoming increasingly popular.
This is, in principle at least, is a good thing, anything that helps the environment and helps us to be a greener company is good with me.
However, in practise what does this actually mean?
Surely, paint is paint
I wish this was the case but unfortunately it’s not, especially with oil-based versus water-based paint products. There are distinct differences between the two and many advantages and disadvantages.
Most of you will already have experience in using oil-based paint on your woodwork, the problem is if you need to do any touch-ups its not as simple as just popping down to the local DIY store, grapping any old tin of gloss and touching up your woodwork.
If you apply a water-based paint product on top of oil-based paint it will not adhere properly, can be chipped super easy and will tend to peel off. This is mainly due to oil and water not mixing. The existing oil-based paint has a water resistant barrier which repels water so when you apply water-based paint over the top of oil-based paint it simply just doesn’t want to stick. The way round this problem is to make sure you key (lightly sand) the existing paint properly, a step most DIY’ers miss.
At Colin Smith Decorating we use Scotchbrite (we prefer Scotchbrite over sandpaper because sandpaper can tare the paint, especially if its been freshly painted), which is an abrasive material very similar to the scouring part of the little sponges most of us have under our kitchen sink
We sand the woodwork with Scotchbrite, which creates very fine scratches in the existing paint, this increases the surface area of the paint which allows for better adhesion between the existing and new paint. After we have keyed the woodwork, we always apply a water-based undercoat first then apply the gloss, satin or eggshell over the top.
What are the key differences between water-based and solvent based paint?
When we refer to oil or water-based paint we are talking about the liquid component of the paint, the part that evaporates as the paint dries. Oil-based paint’s use Turpentine to make up the liquid part of the paint, hence the strong smell. Water-based paints however, as the name suggests, use distilled water to make up the liquid part of the paint
What are VOC’s
Turpentine or more accurately, Turpentine vapours are a type volatile organic compound (VOC) in oil-based paint. As the paint dries the Turpentine evaporate into the air causing VOC’s. This causes damage to the environment and can be harmful to human health if inhaled not to mention its highly flammable. High concentrations have been found to cause headaches, skin irritation and nausea in some people so if you are using the old school oil-based gloss on whatever you are painting please make sure the room is well ventilated and if you are pregnant avoid them completele
As water-based paints dry however, for the most part it is water that evaporates into the air as the paint dries. There is a small amount of VOC’s around 5% depending on the brand, compared to 80% with oil-based paint products
What are the Main Advantages and Dis-advantages of Oil-based-compare to Water-based?
Oil-Based Paint Advantages
• Oil-based paint drags better on a paint brush so tends to be easier to work with
•Oil-based paint usually covers better than water-based although, what brand of paint used also has an influence on coverage.
• Oil-based paints will harden quicker than water-based paint.
•Complete cure time is usually around 1 week.
• Oil-based exterior paints can be used in very low temperatures so outside painting is possible year round.
• Oil-based paint is llightly cheaper than water-based paint. (for wood paint anyway).
Oil-Based Paint Disadvantages
• They Stink!!! Really bad and the smell takes days or sometimes even weeks to dissipate.
• They take longer to dry, usually at least 8-12 hours depending on the brand of paint. This can be a bit of a pain as you need to wait longer to re-coat where needed.
• As mentioned above already oil-based paints contain high amounts of VOC’s which are bad for the environment and human health.
• Cleaning oil based paints is harder because brushes have to be cleaned using another solvent like white spirit. Furthermore if oil-based paint is spilled on a carpet for example, it is difficult to clean up and we always recommend wearing gloves whilst using oil-based paint because its not good for your skin and difficult to clean off.
• THE PAINT WILL YELLOW (especially white wood paint), I have put this in capitals to emphasise this point. We have used every brand of oil-based paint you can imagine, all promising how their paint won’t yellow, DO NOT LISTEN TO THEIR CLAIMS, all oil-based paints will yellow through time some quicker than others and the less light reaching the paint (dark hallways or behind furniture) the quicker the paint will yellow.
• Oil-based paints tend to be stickier so require more effort to apply.
We use Johnstones oil-based gloss. We have tried many brands but find Johnstones oil-based gloss to be the best as it isn’t quite as sticky so flows easier which means it requires less effort to apply it and the finish tend to be smoother with less brush strokes.
We prefer Crown oil-based satin to other brands, firstly because its not as thick as others but , although thinner it covers better than most other brands and is easy to apply. We have even found at times that we can apply it without an undercoat on to previously painted wood work with no issues.
Water-based paint Advantages
• Water-based paints are better for the environment and for our health because they contain substantially lower amounts of VOC’s.
• Water-based paints are touch dry within the hour and are re-coatable after two.
• The sheen from water-based gloss is brighter and will stay brighter for longer.
• Water-based paints don’t yellow, how the paint looks when you apply it, is how it stays, they stand the test of time.
• Water-based paint is cleaned using warm water so brushes and spillages can be cleaned a lot easier.
• Water-based paints don’t have much of a smell so they don’t stink your property out for days or weeks.
• Water-based paints require less effort to apply, as they are not as sticky or thick as oil-based.
• Water-based exterior paints tend to last a lot longer than oil-based paint because they have far better UV protection and can be used in moist conditions where as oil-based can’t, albeit if painting onto a moist surface the paint is slightly thinned as its being applied
Disadvantages of Water-based Paints
• Although they are touch-dry really quickly they take a couple of weeks to completely cure and harden up so fresh paint can be chipped easily.
• Water-based paints don’t cover as well, however if the correct undercoat is used the differences between the two are negligible.
• Water-based paints can’t be used in low temperatures because the paint won’t dry so they can’t be used exteriors all year round (well…. in Central Scotland anyway…).
• The finished result and durability of exterior water-based paint is affected by both hot and cold conditions. We wouldn’t recommend using water-based exterior paints below 6 degrees Celsius or above 20 and never in direct sunlight as this can cause the paint to bubble as it dries. Let me tell you from experience that its no fun having to re-do your entire job due to bubbling paint.
• If painting over varnish, stain, wood knots or a dark colours, no matter how many coats you apply the old colour will bleed through unless you use a solvent based undercoat such as Zinsser B-I-N Stain blocker, hands down the best stain blocker on the market and we have tried them all.
• Slightly more expensive for water-based wood paints around 10-15% more
Gloss We Recommend
We use Johnstones Trade water-based Gloss every day, we prefer using water-based paint over oil-based paint where we can and we feel Johnstones has the best water-based products on the market bar none. This water-based Gloss has an amazing sheen and does not yellow.
Satin We Recommend
We recommend Johnstones water-based Aqua-Satin. We will always try and use this over oil-based satin where we can because it is better for the environment, our health, the paint is re-coatable after two hours and its easy to clean our brushes and kettles at the end of each shift.
Do I have water-based or oil-based paint in my house already
To test if it is water-based or oil-based paint on your woodwork, simply put some methylated spirits on a rag and wipe a small section of the wood. If your cloth is stained with the paint it is water-based paint
At Colin Smith Decorating Ltd. we prefer water-based paint products, for sure. They are environmentally friendly, don’t stink our customers houses out, easy to clean and don’t yellow. The only time we use any oil-based product is when we are working outside in low temperatures or require a stain blocking coat to be applied first
I hope this gives you a an insight into the two products so next time you are down at your local DIY store, remember to read the back of the tin to make sure your buying the best product for the job.