This started as a short teaching project to repair some damage to a small tabletop, but ended up with a full refinish from bare wood, since some of the heat and water marks (see third photo) had penetrated right through.
So, I'll run through things in this order - covering restoration/repair techniques first, and then how to apply a french polish from scratch.
The video shows the techniques much better than just words and photos, but having the written instructable next to you as do your own work will remind you.
Warning: Practice on something worthless until to get the hang of it. It's easy to damage french polish, and end up making more work for yourself (or an expert).
Step 1: Remove Loose Dirt, Food and Paint Splatters, Etc.
Use a flexible card scraper, or old credit card, to give the surface an initial clean
Food and paint splatters can be 'pinged' off at this stage, as they shouldn't be too well attached
Dust off with a brush to reveal any heat or water marks, dings, ink stains, etc.
During this stage, look and listen out for any loose areas of veneer. Photo two shows me tapping an are of loose veneer, which gives a very distinctive, hollow sound compared the rest of the surface. We'll fix that later.
Don't use so much force that you scratch the polish
Step 2: Water and Mild Detergent
Clean the surface with a cloth dampened with water and a mild detergent
Wipe over with a clean cloth and water
Dry with a clean cloth
You may be lucky, and find the surface pristine at this stage, but that's unlikely
Step 3: White (mineral) Spirits
Clean again, this time using white spirits (mineral spirits, US) instead of the water and detergent
This will help remove remaining dirt, old furniture wax, etc.
Leave the spirits to evaporate
You're now down the the French polish
Step 4: Rub Out Blemishes
Blemishes that don't penetrate very far into the polish, can often be removed with the local use of some metal polish or automotive paint polishing compound
Apply a little to the blemished area, and rub gently with a clean cloth
The idea is to cut through a layer of two of the French polish, to a point where the blemish is no longer present
Step 5: Think Carefully!
The proceeding steps are unlikely to cause any real damage, but the following ones can - think carefully whether to proceed, or to call in an expert
If you're just practicing, dive right in and have a go!
Step 6: Removing French Polish
Methylated spirits (denatured alcohol) is a solvent for the shellac based French polish, so applying it to the surface will start to dissolve it
To cut back, or completely remove a French polish, you can use methylated spirits and wire wool. The process is fairly slow, and you may find that all the blemishes disappear before the polish is completely removed. That's great, and you can then begin to build the layers up again (see applying stage later on).
Alternatively, you can quite quickly remove the polish completely by using a card scraper. Done carefully, you can complete this without removing much if any wood (a belt sander for example would likely chew up the wood surface and require a full sanding schedule to prepare the surface for a new polish)
Step 7: Fixing Loose Veneer
Loose veneer can usually be fixed by reactivating the existing glue
Place some plain brown paper over the area, and apply some gentle heat from a domestic iron (set to rayon/low/1). Rub the veneer down whilst hot with a veneer hammer or the softened edge of a hardwood block
If this doesn't work, try wetting the veneer a little first, and then repeating
If this still doesn't work, then try injecting some fresh glue under the veneer, and then clamp (with greaseproof paper on top of the veneer to prevent the clamping block sticking).
Step 8: Applying French Polish - Bodying
French polish is applied using a 'rubber', which is a pad of lint free cloth stuffed with cotton wool
To make the rubber, pack some cotton wool (or soft cotton cloth, etc.) into the centre of a square of lint free cloth. Fold up all the corners of the square, pull tight, and twist
The French polish can either be purchased ready to use in a bottle, or mixed yourself. To mix your own, place shellac flakes in a glass jar, add methylated spirits (denatured alcohol) to cover the flakes, and leave for a day, agitating occasionally. The recommended recipe is a two pound cut, which is the equivalent of 2lb of flakes to 1 gallon of spirits.
Pour the polish into the middle of the rubber and add an equal amount of spirits to thin it. Tighten up the rubber, and check that it is damp but not wet underneath. Remove any excess polish by dabbing on paper
To lubricate the rubber, tap a drop of linseed oil over the pad's surface.
Start applying the polish to the surface. Circles or figure of eight motions work well. You want to move quite quickly, and not let the rubber come to rest on the surface (it will stick). Once fully covered, sweep the rubber in straight strokes, with the grain, across the whole surface
Apply several coats this way, leaving about twenty minutes to dry in between, before moving on
Step 9: Filling Dents and Gouges
Pick a shellac stick of an appropriate colour to match the area of the damage
Clean any dirt or loose material out of the damaged area
Melt the end of the stick with a soldering iron, or a flame, and dab the flowing shellac into the depression
The shellac hardens very quickly, and can be trimmed flush to the surface with a chisel, and sanded smooth with fine abrasive paper
Wiping over the area with a charged rubber will bring it all together
Step 10: Grain Filling
To achieve a glossier finish, it's necessary to fill any pores in the surface. An easy way to do that is to use fine pumice powder
Sprinkle pumice power sparingly over the surface
Use a rubber charged with thinned shellac (perhaps one part 2lb cut, to four parts methylated spirits) to work over the surface in small circles or figures of eight
The pumice both abrades rough areas, and fills the pores, and the little bit of shellac will fix the filler in place
Wipe off excess pumice with a dry cloth or brush, and lightly wipe over with a cloth damp with methylated spirits
Repeat until the surface smoothness meets to your satisfaction
Step 11: Build Up Coats
Continue to apply coats of shellac as in the bodying stage, until the desired depth of finish is reached
Remember to use the linseed oil, and to recharge the rubber before the pad starts to drag too much or stick
Step 12: Spirting Off
To finish off the gloss surface, we 'spirit off'. This removes all traces of the linseed oil
Use a new rubber, and charge with just methylated spirits
Sweep the surface with light passes along the grain
Repeat a few times, using a new area of the rubber's outer cloth
Step 13: Gloss Finish
You should now have achieved a lovely gloss French polish
Leave to cure in a dust free environment for a few days
Step 14: Satin Finish
Leave the finish to cure for a few days
Knock back the surface with a fine abrasive pad or '0000' steel wool (you can apply furniture wax at this stage if you prefer)
Now apply furniture wax and leave for half an hour
Buff the wax off with a soft pad
You should now have a lovely satin finish French polish
Thanks for reading my instructable.