Wood putty, finishing material to fill up the gap and hole

Wood putty is a finishing material used to fill the gap, dent, small holes, cracks or defects in the wood product. Wood putty is substance in the thick paste, and when it applied then he will fill the gaps, cracks, crevices, holes and close them make an even surface. It is almost impossible to eliminate the uses of wood putty in the woodworking industry. No matter how good we control the production process there will be some defects in the wood product. The wood is very unpredictable material, he will move, shrinkage or expand in the processing. The wood properties also may varies from each pieces to the other pieces and very difficult to be controlled. The wood putty is very helpful to do the touch-up process to correct minor defects that often occur in the production process.
Wood putty is made from a bulking agent (the materials which has very little shrinkage) mixed with a binder and then dissolved into a thinner to form a thick paste. The binders used is resin or resin mixture will determine the main characteristics of the putty. There are many different types of putty depend on the binder used; NC, PU, ​​epoxy, water based etc. A good putty can fill the holes well with no (very little) volume shrinkage, but it could absorb the stain color applied thereon. The putty which absorb the stain will reduce the difficulties in the color matching in the finishing process.
According the way of it is used, there are two type of wood putty. The wood putty that is applied on raw wood, and the putty that is applied over the sealer or top coat. The wood putty that is applied to the raw wood is used to do the touch up in the process of assembling or sanding in the unfinished product. This material is applied  to fill cracks and holes and then be sanded to produce a flat and smooth surface. This material sometimes is also used to close the pores and wood grain as filler does, especially for wood with big pores and grain.

While the putty applied over the sealer is the material that is used to touch up in the finishing process. This material is like pastel solid which can be inserted to fill cracks and holes that exist in finishing layer after  sealer application. This putty is inserted in the gap and then flattened with a knife. This material is available in various colors that can be selected directly to match the existing finishing color. This putty can be directly coated with a sealer or top coat thereon. 

Make your own wood putty

There some people prefer to make their own putty even the currently finishing material industry has provided putty with many type and most of them are work well. A simple putty can be made by mixing the sand dust with a sealer or top coat to form a thick paste material. This mixture can be used to fill the holes for the raw wood. We also can mix the sealer with ground silica or other bulking agent to make wood filler.
To fill the small hole or gap on the sealer, we can use a thick dry sealer. Take small amount of sealer then let dry until it form a thick dry sealer, then apply it to fill the small hole as we do with the putty. This thick sealer will have good color match, but its only work for very small hole. To care the big hole we need to do it in the unfinished wood.

Matching colors in the putty application 
 
The problem often found in the uses of putty is matching the color of the putty. The putty in the wood surface often result in different appearance color and looked from the surrounding wood color and we match the color by  touch up. The light area then is hand painted with stain or glaze using a small brush. It is like an artist job that need long time.
However the uses of putty on the finishing process must be minimize as much as possible. The putty should only be used for touch up jobs in the pits and small cracks. Although some types of putty that can absorb the stain of good quality but of course the resulting color will still not perfectly match the color produced from the original timber. The touch up work always take long extra time that is not effective in the mass production. The putty also won’t be able to mimic the appearance of the grain and pores of the wood.

In the furniture industry, the production process should be keep correctly done from the machining process. If there any problem with the component, then the component has to be fixed before it is assembled. The handling in the production process should be done carefully.

To patch the big and wide hole, we better use wood or veneer pieces. Inserting a piece of wood or veneer on the big holes or crack will give better matching looked since the wood piece has grain and pores.