Water-Based Finishes

Water-Based Finishes
We ask ‘are the new generation of water-based lacquers really a match for old school finishes?’

If you think the list of accessible finishing products is a long one then just maybe consider the number of possible outcomes there are when you mix and match the techniques for applying them. My youngest daughter’s maths homework this week was on the subject of probabilities. She’s learned that the chances of getting a Royal Flush in poker are about 2.5 million to 1. Fortunately the chances of achieving a perfect finish are more in your favour and it’s with this in mind that I’ve decided to shorten the odds even more by looking at water-based finishes and whether there is a place in the ‘shop cabinet for a small selection of reliable alternatives to solvent-based products. 

First observations
In the run-up to preparing this article, almost everyone I spoke to about water-based finishes had had a bad experience using them or were either just irrationally averse to trying them, period. Old habits die hard and as I’ve had a foot in both camps in the past I can identify with that. I also know that all it takes is one positive experience for you to adjust your thinking. The most common argument against them was that they don’t go on the same way as oils. That’s true. The second was that they aren’t as hard wearing as oils or lacquers. That’s not true, so before we go any further let’s start by scotching a few rumours about water-based finishes. 

Why use water based anyway?
For a start they are better for us and those around us, which should be a good enough reason to try them out. In many cases the compounds used in their manufacture are the same as those used in solvent-based finishes so it’s the solvent that has been replaced and not always the important stuff. Solvents have a great effect on the way finishing products behave in the tin, while being applied, while they are drying and in some cases long after they have cured. Some oils, alcohol and spirit derived solvents are toxic, unpleasant to use and also require specific arrangements to dispose of excess, so it makes sense to limit our exposure to them. The trouble is we’ve got used to having them around.  

Application
It’s a fact that water-based finishes raise the grain more than oil-based ones. Dampening the surface with a mist of water or a damp cloth, allowing it to dry and re-sanding will generally overcome this. If a thin top coat is your desired outcome, water or oil for that matter, do this at least twice in your surface prep before sanding with a 180g abrasive and then again with 240g. If you’re intending to build a thick layer there’s hardly any point in going finer until you have built up a good layer of product. There will always be exceptions to the rule and I know a lot of finishers that prefer to dive in straightaway with product onto bare wood without going through this procedure, but none of them use water-based finishes.
The first thing you notice when changing over to a water-based product is that it doesn’t lay as flat as oil
straight off the brush. Faced with this the temptation is to rework the product to improve things but because water-based products gel much quicker than oils you end up pulling at the surface while it’s still tacky and making things worse.
The second most obvious difference and the one that catches most folk out is that in warm conditions water-based products do the opposite to what oils do. They tack up even quicker and when it’s  cool or humid they slow down, or worse, stop drying altogether. So if you can get your head around that switch they really do behave in much the same way as oils, just at opposite ends of the warm/cool, dry/humid spectrum.

Water-based effects
The process of liming is effectively the same as grain filling and typically uses a filler that contrasts with the colour of the substrate. For the best effect, timbers with an open grain structure such as oak, ash or elm respond better to the technique than those with a fine grain.
Traditionally the effect was the result of applying a lime paste mixture to hardwood surfaces to ward off attacks from bugs and beetles. The caustic nature of lime means this method is no longer practised. However, the appearance of lime has been a popular decorative style falling in and out of fashion for the last couple of centuries.
First of all if you want to achieve that look nowadays, it’s not difficult and won’t strip the skin off your hands either. The simplest option is to source a proprietary liming paste. These are generally wax-based pastes that are applied to the surface and require little or no further treatment. They also offer little or no protection from the rigours of daily life.
Step things up a notch and you can seal over the filler with a protective coating of your choice for a more durable surface. I don’t want to cover every possible permutation in this article, you wouldn’t thank me for it, so instead I’m going to focus on an effect that mimics that of liming with acrylic milk paints. I’ve chosen those made by General Finishes. Just so we’re clear, this is not liming but a technique that mimics the effect of liming.

Preparation
Preparation as they say is everything and for a limed appearance that means scrubbing the surface with a coarse brush, preferably a wire one to remove all the pith and dust from the grain of the wood. Sanding might have been a good idea up until now but once you have brushed the surface don’t touch it again with any abrasive. Instead, reach for the vacuum and remove all the loose particles from the surface. If you like the idea of surface preparation without the use of abrasives then now’s a good time to try it out. A finely set smoothing plane or card scraper will serve you well.

Laying down colour
Strictly speaking paint isn’t the best medium for liming. It can dry before you have had time to force the solids into the grain and wiping the excess off has to be done quickly. And given that the colour in paint is partly due to the use of dyes and not pigments, staining the surface is a real possibility. It would be wrong to suggest that some colours work better than others as colour is subjective in terms of quality. It’s not even fair to assume that better quality solids or pigments or a higher density of them will result in a better paint for liming. To get the paint into the open grain, work the brush or pad across as well as along the grain. Air gaps and dust in the grain will cause bubbles to appear so you’ll need to be vigilant to achieve an even look. Before the paint dries take a clean cloth and wipe away the excess. Dampen the cloth with water if the paint begins to dry. Although this won’t offer a great deal of protection to the surface of the wood, it may be the finish you want. For something a little more robust recoat with something like a General Finishes clear Top Coat. 

Water-based finishes in general
Water-based finishes take longer to dry than you think. If it says dry in 30 minutes that’s really all it means. Dry is not the same as cured and this can take up to a week in low temperatures and four days under normal conditions for some products although it probably wont say that on the tin. During that time, however, the products are typically safe to handle and it’s really only excess moisture that you will have to avoid. Try to resist the temptation to apply wax until the product has cured. It will only slow things down and be equally cautious about burnishing or rubbing out too soon after application. There were a couple of products that really stood out for me while compiling this article; General Finishes Enduro-Var and Liberon’s Water based Hardwax Oil.

Enduro-Var
This urethane varnish is quick to build and is remarkably self-levelling. A foam applicator is the best method for applying by hand but a brush works just as well. It tacks up quite quickly so you need to work fast on large areas if you are applying by hand. It sprays straight from the tin so there’s no need to thin. In fact doing so could affect its performance. The product is translucent and slightly pink in colour but this is not transferred to the timber. On pale timbers you may initially experience some slight warming of the general tone but this fades as the product dries. Sanding between coats is recommended and a pre-sealer is not required. It offers a good level of protection for interior use although not in very wet areas and resists scratches.

Hard wax oil
You wouldn’t usually expect to find the words water, oil and wax in the same sentence let alone in the same tin but that’s what Liberon have done and it works a treat. Unlike solvent-based HWO this isn’t a saturation product meaning it doesn’t crosslink with the wood. Instead it becomes a membrane-like layer like a traditional varnish or lacquer. It goes on with a brush and skins over quickly just like shellac so try to avoid overlapping brush strokes. It has a milky white appearance on application but soon clears and when it does, unlike oil-based HWOs, it won’t cast a yellow hue. Sanding between coats is recommended but not nearly as important as wetting and sanding before applying the first coat. For a quick drying general purpose finish on interior work it’ll give oil-based HWO a run for its money.

Quick dry varnish
By fine finishing standards this is crude but effective. It builds to a very thick coat easily, is less susceptible to runs on vertical faces than the other water-based finishes I tried and more so than oil varnishes. I applied this with a cloth French polish style on a new handrail where the window of opportunity for finishing was limited. Even though it says quick dry on the tin you do need to wait a couple of hours before re-coating. Despite this the job was completed in a day with a minimum of disruption to other trades. To slow the drying time down and to help with work in higher temperatures the instructions suggest thinning with water by 10%. That’s good to know but perhaps best left for horizontal surfaces only. Like all the other water based finishes it’s virtually odourless and brushes or rollers can be cleaned with water.

Water-based for outside
Exterior work is perhaps where you have to be a little more cautious about where and when to apply. Your working conditions are likely to be more extreme and avoid the end of the day if you suspect a dewy evening or rain. My experience with exterior water-based products is limited to garden furniture. It’s the one and only time I’ve used a varnish/stain combination. By my reckoning they seem to be aimed at the DIY/amateur market as an easy fix for tired old timber. Over-coating is a real problem if you want to avoid patchy areas that obliterate the character of the wood. For extra protection consider applying a clear top coat to build up layers.

Conclusion
If you were to base your choice of finish purely on ease of use then water-based products should win hands down every time, although they’re a long way from replacing oil and solvent-based ones for the majority of new interior fixtures and fittings. For post-installation flooring products however, the split is around 50/50. Water-based finishes result in a surface film being applied much like a traditional varnish or lacquer so good surface preparation to ensure reliable initial adhesion is important. They can appear at first to be rather cold on virgin timber but this it’s often short lived as the wood changes colour on exposure to UV light anyway. The only difference being that the change you see is in the colour of the wood and not the finish.