French polish, the classic method of applying shellac

I promised you when I wrote about shellac, that I'm going to revisit the subject to say more about French polish - special method of applying this natural varnish. I don't forget the promise, so the following are a series of details and tips that are sure to make you want to varnish at least a small piece of wood using this method. At least with me that was the reaction.

The shellac application process is time-consuming, repetitive and labour-intensive. Application techniques are very much up to the individual specialist, with experience gained over time helping them to find the method that best suits their way of working. Regardless of the technique used, there are some common elements: preparation of the varnish, the substrate, the pad to be applied and the mandatory principles during application.

The first operation is getting the varnishfrom flakes. As you have seen, shellac is mostly sold in solid form because it does not last very long ready-made. Shellac is also available, but it contains a number of additives that prolong its life and can affect the final quality. It is therefore best to have the varnish prepared by the person applying it. Shellac flakes or buttons dissolve in denatured spirit (industrial alcohol). There are several proportions in which dilution can be done, but the most commonly used are:

• 350-360 g/l of alcohol - for applications as a first coat (primer or primer) or for painting applications, for substrate preparation. In this case only dewaxed shellac is used;
• 240-250 g/l of alcohol - the most used proportion for application and sanding;
• 100-120 g/l of alcohol - the final coats that are applied without intermediate sanding and that give the mirror shine.

Choose the flakes according to the desired colour and grind them finely in a food mill to dissolve them more easily.

It's best to use glass containers with lids to stir the mixture. Do not use metal containers because they interact with the components. After weighing, measuring and mixing, put the lid on, shake the mixture well and allow 1-2 days for complete dissolution. Finally filter through a fine sieve to remove impurities. If it's a cold spell, for faster dissolution, you can put the varnish pot in a bowl of warm water. Be careful not to put the vat directly on the fire or in boiling water as the high temperature will spoil the varnish.

The next step is buffer preparation with which the application is made, what do they call it specialists. It can be made from cotton wool, pieces of old knitted or woollen bumbarc, which are put in a piece of finet or cotton, tightened tightly and knotted so that they do not fall apart during application. Finally, the pad is tapped a few times against a flat surface to weave and settle. The underside should be tight and flat, without creases, seams or holes, which can cause the varnish to be applied unevenly.

Before varnish application the surface of the wood must be prepared and sandedvery well. Scratches and holes are repaired. If the finish is to be satin-finished, sand large-pored hardwood (walnut, oak) with 400-grit sandpaper and smaller-pored fine wood (palisander) with 600. For mirror polish, use 600 and 800 grit paper respectively. Musical instruments are sanded with 1000.

Varnish loading of the pad is done with great care and by pouring the lake little by little. It is best to use a pipette. The swab must not be mushy, but neither must it be dry. It can be tested on the back of the palm, where it should feel moist and the varnish should not run off. Finally, put a few drops of mineral oilwalnut or olive oil. Linseed oil is not good because it is too viscous. The oil helps the pad to glide, and the varnish doesn't get caught on the wood in large quantities. Loading the pad is when experience tells. You will only know the right amount of varnish or oil once you start working. If the pad gets stuck on the surface, it means too much varnish or too little oil has been applied.

All ready to go the actual application of the varnish, with continuous circular or figure 8 movements. Never stop because a dent will appear there. Even if varnish drips from the pad, the movement must not stop. Continue moving towards the edge. The stopping should not be done suddenly but as a continuation of the movement. The turning of the hand practically brings you to the edge of the piece.

Shellac dries quickly compared to other varnishes or oil, in 5-10 min. After each application the surface is sanded to remove any unevenness. Even if it dries in 5 min. it is better to sand after 20-30 min. Sand with 800 grit at first, then continue with 1000, 1200 or fine steel wool. Even 30 or more coats are needed to achieve a beautiful surface. For mirror gloss, use thinner varnish for the last coats and do not sand between coats.

Applying shellac is no simple matter and it's best to call in specialist firms if the project involves old pieces of furniture that need to come out perfectly. Just like in the article about recovering 100-year-old furniture.