Prevent cupping timber with Dale Glass Industries' Glulam

Cupping is natural and occurs when there is an absorption or loss of atmospheric moisture on one side of the board and not the other, causing a moisture content imbalance. This imbalance is a temporary situation and is caused when there are changes in humidity or atmospheric conditions. Proper sealing prevents an imbalance occurring.

Cupping can be corrected by reversing the cause; ie. turn the board over and just leave it, or strip the boards out so air can circulate evenly. If time doesn't allow this, then the correction process can be hurried by wetting the dry side. This creates artificially high humidity and the dry side will absorb moisture until both sides are in equilibrium and the board is again straight.

The drier side is always the concave side. Place the board with the concave (dish) side up and on gluts so air can circulate (This also helps to dry out the wet side). Pour water on to the top (into the dish) until it pools evenly across the whole board. Lay plastic over the top so the water doesn't evaporate too quickly and leave it. The bigger the cup, the longer it will take to correct, but check it after an hour or two for progress. After the correction is completed, the water will have raised the wood fibres so it may be necessary to lightly sand again. Seal the board as soon as possible.

Endsplits
If "GLULAM" is left unsealed, it is possible for the board to loose excess moisture via the end grain particularly when the temperature exceeds 25°C. This moisture loss can cause minor openings of the gluelines at the ends of the board. This is a common occurrence and is no indication of glue failure or delamination.

To obviate the problem before it occurs, ensure that the ends of the board are well sealed. To repair minor endsplits fill with clear silicon (eg. Silastic) and seal: the splits should then close naturally. If the end splits are longer, let some full strength Epoxy glue flow into the split/s, clamp and allow to cure before sealing. A strip of tape underneath the glueline stops glue loss.

Minor Dents
A small dent can be easily fixed by recovering the crushed wood cells with an application of steam. To achieve this place a very damp rag over the dent and sit a hot iron on the damp rag. Allow the wet heat to penetrate the timber. The time for it to recover will vary according to the severity of the dent and the density of the timber. Check on progress after a minute or two and if necessary repeat. Finish with a light sand particularly if the wood fibres have been broken or damaged. This process can also be done over a finish but takes longer.

Natural Timber Blemishes
Any grain checking, tearout and similar timber blemishes can be filled with a matching wood putty and then sanded smooth. Shakes and similar blemishes which have a tendency to lift can be glued down using a five minute Epoxy glue mixed with matching colour sanding dust.

Alternatively, to make a blemish appear natural, apply "Plastibond" coloured with a very small amount of oxide of suitable colour. Sand smooth when it has set. If filling as above is impractical because of aesthetics, a portion of the laminate (approx 3mm deep) can be removed with a router and replaced with a fillet (a strip of similar timber ripped to the matching width and thickness) glued in place with a full strength Epoxy glue, and then sanded.

Remove Stains
Sanding will remove most stains, however in some timbers, tannin stains and water stains are stubborn. Soak the surface to be cleaned with clean water, mix Oxalic Acid with water as per the instructions on the pack, then brush the solution on and allow it to react for about two hours. Wash down the surface and allow it to dry. If the stain is still visible then repeat the process. When stain free, fine sand.