Seasonal hints and tips from the professionals
As the northern hemisphere winter draws in, there’s no need to stop those DIY epoxy projects at the boatyard – just make allowances for the lower temperatures and seasonal damp conditions.
Keep your resin and hardener warm
Epoxy resin and hardener is very susceptible to cold and should not be stored below 10ºC. For best results, aim to keep it at around 18-22ºC (room temperature). This amount of warmth makes the resin and hardener very fluid and easy to pump, pour and mix. As the temperature drops, so the resin thickens and the cure time extends. Epoxy shouldn’t be used below around 5ºC unless you can warm up both the resin and hardener as well as the job it’s going onto.
Make yourself a ‘hot box.’
Professional applicators and DIY enthusiasts will invariably make themselves a hot box (and in big volume yards, a ‘hot room’). These are easy to create with DIY tools and consist of an insulated wooden box, chest or cupboard fitted with shelves and heated by a 40-60 Watt filament bulb connected to a thermostat. Mike Falcon (see Grey Falcon restoration feature here) suggests that a heating mat for a reptile cage is equally efficient.
Old wooden packing cases can all be converted into a hot box with minimal effort but just make sure they have a door. For energy savings, line the inside of the box with some silver-backed radiator insulation.
Bring your epoxy indoors
If you haven’t yet made yourself a hot box, then bring the epoxy indoors and store it in a utility space or an under stairs cupboard for the winter. When driving to the boat, the epoxy can be positioned in a crate near a heating outlet in the floor-well to keep it warm.
If the frosts have crept up on you, then you might find that the resin you have left in the boat or unheated workshop has crystallised. This isn’t a major problem, as it can be returned to a liquid state by sitting the container in a basin of hot water. Take the lid off to allow for expansion and make sure that no water can get into the resin container as you stir the contents with a long, clean stick. The warmth will dissolve the crystals, with no harm being done to the epoxy chemistry. After the crystals have disappeared, put the top back on and invert the container to clear the last remaining crystals from the neck. Keep the resin and hardener in a warm place after that and they should be fine.
The Ikea-style curing oven
Warm air on plywood
If applying a coat of epoxy to a plywood sheet on a cold day, gently warm the surface with an electric blowgun or hair dryer before applying the first layer of epoxy. This has several benefits. Firstly, it displaces any surface moisture. Secondly, the warm surface and equally warm epoxy will reduce the cure time and ensure mixed epoxy resin remains easy to work. Thirdly and perhaps most important of all, as the plywood cools again it will literally suck the resin into the porous structure, aiding the impregnation of the fibres.
However, the reverse is also true. Don’t apply epoxy if the plywood is likely to heat up from direct sunlight on a bright winters day, as the air trapped in the fibres will outgas, causing your layer to be covered with tiny air bubbles.
Dehumidify the boat
If working inside a boat during the winter, use a dehumidifier, or at least have some heat going. This will help to remove some of the moisture from the air and reduce the formation of amine blush, especially if you have to leave each coat to cure between other jobs.
Amine blush is a by-product of the curing process and is encouraged by damp air. Amine blush looks like a layer of condensation on the cured glossy surface but is easily washed away with warm water and a soft scourer.
Boat builders tend to use oil-filled bar heaters on board as they give a good, consistent warmth. They are also safe to work around and to leave on for long periods and are relatively efficient when compared with other types of electric heating.
Incidentally, marinas in Europe (and especially in the UK) are not allowed to charge excessively for the power you use, as these tariffs are regulated. However, some will insist you buy or rent a metered cable so they can accurately bill your account. (Cable price £80-£120).
Remove peel ply at the last minute
Peel ply is a tightly woven synthetic fabric that is applied to a freshly coated surface and is literally bonded into place as the epoxy cures. As the peel ply is made from slippery nylon, epoxy can only form a weak bond with it. This makes the material easy to peel away (hence the name) once the epoxy has cured. The result is a rough epoxy surface free from amine blush, ideal for the application of primers or fillers with no need for further sanding. Peel ply is a great time saver and is widely used on the last coat of epoxy before the primer stage.
However, in a tip from Compass Tenders, the makers of high-class runabouts for superyachts, the trick is to only peel as soon as you are ready to prime or paint and not a moment later.
“Once the ply is removed, the underlying coat is exposed to the elements and can pick up dust, contaminants and other airborne pollutants very quickly, however clean you think the workplace may be,” a craftsman told us. “As such, we leave the ply on to the very last minute, as it forms a natural protective barrier. We only take it off the moment we are ready for the next phase. This helps keep the exposed substrate in peak condition.”
In fact, despite using peel ply, Compass Tenders still sand the ply peeled epoxy surface to guarantee 100% adhesion, using the peel ply as an aid to the sanding process rather than as a direct replacement. To many, this additional sanding may seem unnecessary but then some of the bespoke designs from Compass Tenders can sell for upwards of £1 million apiece (www.compasstenders.co.uk) so perfection is the name of the game.