Painting and
finishing,
properly.

The short version

Two things run this entire stage.

There is a learning curve here you cannot shortcut. You are going to make a mess of something. Practice on anything other than the guitar first.

The numbers, in one place

Item	Figure	Note
Final grit on bare wood	220	Going finer can make the wood reject finish
Fretboards and detail work	320 to 1200	Only where you want glass
Wet sanding clear coat	1500	Starting at 800 leaves scratches you then have to chase
Primer coats	3 to 4 thin	Sanded between
Clear coats	3 minimum	Two is pushing it. One will not survive buffing.
Clear coat mix	~4:1 with hardener, plus reducer	Aim for the consistency of milk
Paint reduction	~2:1	Check the tin
Respirator	Cheap	Charcoal filters. Not a dust mask.
HVLP spray gun	Cheap one works, pro one costs many times more	You do not need the pro one
Inline air filter	A couple of bucks	Branded sellers charge many times that for the same part
Foam sanding block	Cheap	Automotive paint supplier. Lasts for years.
Soak wet paper before use	15 to 20 minutes
Buffing pressure	1 to 2 lb	More generates heat and burns through

Sanding

The grits

Lower number, coarser paper. The working sequence on bare wood is 60, 80, 150, 220, and you do not always need to start at 60. On wood that is already close, 220 alone may be enough.

Go finer only where you want glass and are not relying on absorption, like fretboards or resin inlay. Past 1200 you are into steel wool territory.

Always with the grain

Grain direction is fiber direction. Sand across it and you tear the fibers, and those scratches never come out. You can go 80, 150, 220 over cross grain damage and still see it under the finish.

The place people meet this most is cleaning a fretboard with the frets installed. Do not run the paper across it. Fold the paper and butt it up against each fret, working along the board.

Where a section's grain runs the other way, turn and sand that way. There is no shortcut.

Paper wears out

Grit dissipates with use. A well used 80 grit behaves more like 100 or 120. A fresh 150 will often remove more than a tired 80. If it feels like you have been sanding one area forever, the paper is the problem, not you.

Blocks

Sanding by hand without a block gives you dips, because people settle in one spot and work it. You can spot a hand sanded body from across a room.

For wet sanding, use a foam block instead. It is more forgiving over edges, and because the foam compresses, not all of your hand pressure reaches the surface, so it moderates how deep the grit bites.

Paper types

• Standard paper for bare wood and primer.
• Black wet or dry for wet sanding. It survives water, and you can rinse the swarf out.
• The best finishing papers come from automotive paint suppliers, the places that supply body shops, not the chain auto parts stores. Expensive, and worth it.

The water test

This is the most useful technique on this whole page, and it costs nothing.

It shows you, instantly and mercilessly:

• Cross grain scratches you could not see dry.
• Burn marks left by router bits.
• Glue squeeze out. Glue will not absorb, so it stays pale while everything around it darkens.
• How much darker the end grain is going to go.
• How much figure will pop. Flame in particular jumps dramatically when wet.

Rough areas take on more water and dry slower, because there is more surface area for it to soak into. Smooth areas dry first and look lighter.

The catch: water raises the grain. The fibers swell and stand up, so the area that felt smooth will feel rough once dry. Knock it back with 320 and you are ready to finish, and now you actually know you are ready.

End grain, conditioner and sealer

End grain absorbs far more than face grain, so it finishes noticeably darker. Sometimes subtly, sometimes dramatically.

• If you are staining: use a wood conditioner first. It evens out absorption so the stain takes uniformly instead of blotching. Sold right alongside the stains in any hardware store.
• If you are only clear coating: a sanding sealer does the same job. It seals the end grain, and it doubles as another way to see imperfections before you commit.

Grain filler, usually not needed

On a natural finish, grain filler causes more problems than it solves. It does not take stain or dye like the surrounding wood. It either goes too dark, or the resins in it reject color entirely and you get pale speckles.

Two better routes:

• Natural finish: multiple thin clear coats. Build them up and the clear coat becomes the grain filler by the time you wet sand.
• Paint grade: the primer is the grain filler. Spray it heavy where you need fill, and sand it back.

Plenty of builders skip filling entirely and leave the grain readable through the clear. That is a legitimate look, not a failure.

If you do want filler, put it on very thin and wipe most of it back off. It can be colored, and some people use drywall mud with dye mixed into it.

Paint grade is a different standard

What never to use

Hardware store polyurethane in a can is also off the list.

The exception is specialist aerosols for effects you cannot get any other way, and that is a deliberate choice, not a convenience.

What is allowed

• Lacquer sanding sealer. Easy to get, dries fast, ideal under tinting on a maple neck. Spray, sand at 320 to 400, then color.
• Aerosol lacquer. Genuinely usable, unlike spray paint. Expect six or seven coats to build enough film to wet sand. Very thin coats, and the surface has to be perfectly prepared first.

Lacquer versus urethane

	Lacquer	Urethane
How it hardens	Dries, the solvent evaporates	Cures, a chemical reaction
Time	~30 minutes	24 hours or more
Toughness	Softer, less resilient	Very tough. Think plastic.
Yellowing	Yellows over time	Generally does not
Between coats	Each coat melts into the last and fuses into one film	Bonds, but does not truly burn in
If you sand through	No visible layers	You see the layers, and cannot buff them out

Neither is better in the abstract. I keep lacquer for matching an existing lacquer finish or working on vintage instruments. Urethane is what I use for everything else.

Stain versus dye

These are not two words for the same thing, and the difference decides what you can do.

Stain

Pigment particles carried in a solvent, plus a binder, which is essentially a glue that holds the pigment to the wood. Without it the color would rub straight off. What you get is a thin, semi-transparent film sitting mostly on the surface.

• Stir it thoroughly, and keep stirring. The pigment settles into a clump at the bottom of the tin. Without stirring you are applying solvent and binder and no color.
• Put it on, leave it a few minutes to soak in, then wipe the excess with a dry rag.
• A second coat absorbs less, because the binder from the first is in the way.
• End grain drinks it, so use a conditioner.
• Removing it means letting it cure fully and sanding it off.

Dye

No pigment. Think of it as a salt that dissolves into water or alcohol, leaving very fine transparent particles in suspension. No binder. Once dry it leaves what is almost a dust, and it will come off on your finger.

• Dye penetrates far deeper than stain.
• It is the best way to make figure pop. Flame absorbs differently to the surrounding wood, so the contrast increases.
• Alcohol as the carrier evaporates faster, so you work quicker with less penetration.
• A single packet makes several containers and will color a great many guitars.

The sand back technique

Dye it dark first. Let it dry. Sand the surface back, and the dark stays down in the figure while the flat areas lighten. Then put a second, lighter color, say yellow, over the top.

The result has real depth, because you are looking through one color at another. This is how those dramatic figured tops get done.

Mixing your own colors

Spend a few bucks on artist's acrylics and learn this properly. It applies equally to dyes and paints.

• Buy primaries. Ask specifically, because many reds and blues have other colors mixed into them. Look for tubes labeled "primary".
• A color looks different depending on what is next to it. A blue with a little red in it reads as blue on its own, and obviously purple beside a true blue. Train your eye by comparison.
• Colors are not equally dominant. Red and blue are strong. Yellow and white are weak. A trace of blue will take over a large amount of yellow.

Secondaries: yellow and blue make green, yellow and red make orange, blue and red make purple.

Browns: take any secondary and add the primary you left out. That is all a brown is.

Tape

Tape	Verdict
Ordinary masking tape	Never. Absorbs paint, leaves gum, hard to remove, reacts badly with solvents.
Painter's tape	Fine for masking areas where the edge does not matter. Comes off cleanly. But its texture lets paint creep under, giving a jagged line. Reacts badly to water.
Automotive fine line tape	Paint will not creep under. Clean, sharp lines. From automotive paint suppliers.
Frog Tape	Adhesion is slightly less than fine line, but it gives straighter lines than the others, removes easily, and resists solvents well.

Do not cheap out on tape. It is the least expensive part of the job and it decides your edges.

Safety

Check before every use:

• The inhale and exhale valves are clean, uncracked and moving.
• The filters are not saturated. Replace them on the manufacturer's schedule.
• You are clean shaven where the mask seals. Facial hair breaks the seal and the mask does nothing.

Gloves: solvents eat most of them. Nitrile gives you roughly thirty seconds against acetone before it starts coming through. Latex is not adequate. Use chemical resistant gloves and change them.

Even water based dyes soak into skin and take days to wear off, and some of what they are made from is not something you want in you.

Ventilation, always. Sensitization is permanent, and once it happens you may not be able to be in the same room as the material again.

Equipment

Guns

Professional HVLP guns are excellent and last for years. They are also not required. A cheap gun will spray primer, paint and clear perfectly well, and even a tiny 4 oz gun will do a guitar.

Air

A pressure regulator at the gun is far more convenient than walking back to the compressor, and you will be changing pressure between primer, paint and clear because the viscosities differ. Start at the manufacturer's recommendation, then adjust to what works.

A blow gun clears dust out of the pores before you spray.

Cleaning

Gun controls

• Air cap rotates to switch the fan between vertical and horizontal.
• Fluid control sets how much material feeds through.
• Pattern control sets a tight circle versus a fan. Never spray with a tight circle, it is close to a guaranteed run. You want a fan.
• Air control, plus a lock to hold your settings once you have them dialled in.

Always test on cardboard or scrap first and dial the gun in before the guitar comes anywhere near it.

Filtering and mixing

Strain your paint through a fine mesh cone before it goes into the cup. Paint suppliers hand these out free. There is a second filter in the gun, but the first one is what catches the lumps.

Use graduated mixing cups with ratio markings. Not styrofoam or paper cups. You cannot measure with them and solvents go straight through them.

Tack cloth

A lint free cloth with a gummy surface that lifts fine dust, lint and hair. Use it before the clear coat. Not needed before primer. Wipe gently, do not scrub.

Paint

Automotive paint systems. Ask your supplier how each product is meant to be applied, because they genuinely differ.

• Candy colors are transparent, so whatever is underneath still shows through. Ideal over figured maple, where you are adding a hue instead of covering.
• Metallics carry fine metal flake in suspension.
• Fluorescents and many transparents need a base coat, usually white. Light passes through them, hits the base and reflects back. Sprayed straight onto black, they barely register.
• Heavy metal flake needs a gun made for it.

Quart containers are pure paint with no reducer. Small airbrush bottles usually come pre thinned. Typical reduction is around 2:1, but check the tin.

Reducers

Reducer is thinner, and it is graded by temperature, not by paint:

• Fast, for cold conditions.
• Medium, roughly 68 to 80°F, most of the time.
• Slow, for hot conditions.

Automotive paint dries very fast, often under a minute, and it is ready for clear within about five.

Primer

Polyester primer with a catalyst, a few drops per ounce. Stir it exceptionally well, because the pigment settles hard, then thin it with reducer or acetone.

• Three or four thin coats, not one thick one. If it will not come out of the gun, it is too thick, so pour it back out and thin it.
• Sand between coats with 220.
• Primer is the one place you can deliberately go heavy. Spray it thick over a low spot, let it fill, and sand it flat. It is your grain filler and your last chance to fill defects.
• Bondo anything the primer will not fill.
• The final coat only needs to be thick enough to cover uniformly.

Inspect after every coat, closely, in good light. Anything you find now is something you will not have to look at forever afterward.

Spraying

1. Hold the gun square to the surface, not angled.
2. Start the spray off the work and move onto it, and carry on past the far edge before you release. Starting on the work is how you get runs.
3. Keep moving. Dwelling in one place builds material and drips.
4. Do not go for full coverage in one pass. Build it.
5. Inspect between coats for misses.

Sanding scratches and light orange peel in the color coat will disappear under clear. What matters at this stage is complete, even coverage.

For handling, a block of wood with two screws into the pickup cavity gives you a handle, so you can spray a body all the way round without touching it, then hang it by a tuner hole.

Clear coat

2K urethane, mixed with hardener at around 4:1 and reduced to roughly the consistency of milk, or a hair thicker.

Layer while the previous coat is slightly tacky, exactly like the paint.

A lot of manufacturers ship guitars with the orange peel left in the clear, and most customers never notice. Wet sanding and buffing is what turns that into glass.

Repairs

Because urethane does not burn into itself the way lacquer does, a repair coat leaves a visible boundary. A fade out, or blending, solvent sprayed over the repair keeps the clear active longer so it melts into the surrounding finish.

Essential on dark colors, where every boundary shows.

Wet sanding

Foam block, 1500 grit, both soaked in water for 15 to 20 minutes first. A drop of dish soap in the water acts as a lubricant if you want it. Keep water beside you the whole time.

The target: the whole surface uniformly gray, foggy and dead flat, with no bumps anywhere. Wipe the water off and let it evaporate to inspect. The shiny specks left behind are the low spots you have not reached yet.

Starting coarser than 1500 is usually a mistake. 800 grit leaves scratches you then spend far longer chasing, and on a black finish every one of them shows.

Buffing

Buffing is basically heated sanding. Compounds are graded like abrasives, strong cut, polishing, intensive, final, super finish, and they behave like grits from roughly 800 up to 2500.

• Super finish for paint. The coarser compounds get used for frets and metal.
• Dedicate one wheel per compound. Wheels accumulate compound, and a contaminated wheel will not give you the finish it is supposed to.
• Soft cotton wheels for the final finish. The denser, more aggressive wheels increase your chances of burning through.
• Load the wheel with compound before you start.

The safety rule that matters most

Heat

Roughly one to two pounds of pressure. More pressure and slower movement builds heat, and heat burns straight through the clear.

Lacquer burns through much faster than urethane, so keep moving.

Working it

Keep lifting the body and inspecting it against the light. A surface can look glossy and still be full of fine scratches, and you will only catch them at the right angle. Where scratches remain, buff across them rather than along.

Settings matter more than you would expect. In my shop that means the lowest speed and exactly two soft pads per side. More pads slow the wheel too much to make the friction you need, and a single pad makes burn through far more likely. Your machine will want something different, and the only way to find it is testing on something that does not matter.

What to expect

The difference between a raw, rippled finish and one that looks like glass is entirely in the wet sanding and the buffing. It is the last stage of the build, and it is the one people see first.