A brief outline of how to use epoxy.
The epoxy as supplied with the kit was Professional Epoxy Coatings. This is amazing stuff - it does not smell and you can wash any splashes off your hands with soap and warm water. The technical information does not mean a great deal to me but it certainly sets very hard. Ensuring an accurate ratio of the two components is important for getting the maximum strength and the use of measuring pumps makes this easy as well as less messy. At about 15 degrees the working time is about 30 minutes which is more than enough time for even a timid builder like me.
Wear goggles to prevent splashing your eyes. Always wear disposable gloves when working with epoxy since the parts contain potentially dangerous chemicals. Any spills of this epoxy can be cleaned using soap and water or vinegar or, better still, a hand cleaner.
Fit the correct pumps into the epoxy containers.
- Pump the resin into a mixing container. Depress the pump only once
- Pump the hardener into the mixing container. Depress the pump only once.
- Mix the two parts together thoroughly with a stick for 1 minute
- If required, mix in wood flour and silica powder to thicken
In General epoxy cures quicker the warmer it is kept.
Try to keep the workshop above 15 º C. The epoxy will cure below this temperature but it may take days. Warming the resin and hardener by keeping it near a source of gentle flame-free heat helps but do not attempt to warm it after mixing as it will probably set before it can be applied. Joints
If correctly mixed and applied the epoxy forms a bond that is stronger than the wood itself. In positions where epoxy is likely to run or drip out of the joints then it is advisable to thicken it by mixing in silica powder and wood flour until it forms a paste. The colour of the epoxy can be matched to the colour of the wood by altering the ratio of silica to wood flour. If the mixture is too thin it will squeeze out of the joint when the clamps are applied, if it is too thick it will form an uneven bump in the wood. It should be made to a similar consistency as lemon curd, that is, it should run but not flow of its own accord. The application of gentle heat from a hair dryer greatly speeds up the curing time but beware of burning the wood. The longer the clamps or weights can be left in place the better: try to leave them at least 24 hours.
Cleaning hardened epoxy off joints is a tedious job. Avoid the work by wiping away as much epoxy as possible before it sets. For a really easy clean up job run some plastic sealing tape along the outside edges of the joint before applying the epoxy; when the epoxy is cured remove the tape along with the excess.
Large gaps in joints can be filled with a fillet of epoxy. For gaps up to 5 mm the epoxy can simply be pushed into the gap with a palette knife. Larger gaps are best made smaller by inserting wedges or fillets of wood then using epoxy.
Filleting is recommended whenever water proof seals are required. To provide the bulk, wood flour and silica powder should be mixed with the epoxy. The colour of the epoxy can be matched to the colour of the wood by altering the ratio of silica to wood flour. Unfortunately, epoxy that seems thick in the pot often starts to sag after a few minutes as a fillet. If it sags return it to the pot and thicken a little more. Keep thickening until the epoxy stands up on the mixing stick like thick porridge.
Fillets should be concave in section and between 5 and 20 mm across. The width will depend upon the location. To achieve a smooth curve use a curved stick or tongue depressor.
The epoxy needs to be coated thinly and evenly on the wooden surfaces. The best way to achieve a good finish seems to be to use a roller. Inexpensive sponge rollers work well and are thrown away after one use. The most likely cause of problems is over brushing or rolling: the first pass gives the best finish. At least two coats need tobe applied. If the second coat is applied within 5 hours of the first it is not necessary to prepare the surface other than to ensure it is dust free. If more than 6 hours have elapsed the surface will have to be lightly sanded to provide a key for the second coat.
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