Cruising with sailing vessel Phoenix

Varnishing 101

Step 1: Go read Rebecca Wittman's book, Brightwork: The Art of Finishing Wood - it has everything. The notes below are just a simplified distillation of what I learned from her book.

Varnishing has four types of processes after the surface is basically clean and ready to go. (If you still need to remove old or peeling varnish, get a heat gun and read The Book, above). These four processes are Preparation, Priming, Sanding, and Varnishing and are applied in the following step-wise order:

Step	Coat	Directions	Application method
Preparation		Make sure surface is clean, dry, and sanded smooth to at least 120 grit
Priming	1	Cut varnish with spirits 2-1 (two parts varnish, 1 part spirits).	Wait 4 hours to next coat
	2	Cut varnish with spirits 4-1	Wait 4 hours to next coat
Varnish	1	Cut varnish with 15% to 25% spirits	Plaid Wait 24 hours to next coat
Sanding		220 grit - lightly
Varnish	2	Cut varnish 10% - 15% spirits	Plaid
Sanding		220 grit - lightly
Varnish	3	Full strength	Plaid
Sanding		220 grit - moderate
Varnish	4	Full strength	With-the-grain
Sanding		220 grit - heavy; surface should be completely white
Varnish	5 - 10 or more	Full strength	With-the-grain 24-48 hours to next coat
Sanding		320 grit - lightly. After 7th or 8th coat wait at least 48 hrs before sanding
Varnish	final	Full strength	With-the-grain

Preparation

You will never fix roughness or grain problems with varnishing, so make sure the sanding is beautifully and completely done before you start. For furniture grade and for rougher grains like mahogany, you may even want to use a filler to get a smoother surface. Read the Wittman book for these details. Otherwise, sand to at least 120 grit before beginning the varnish coats.

Priming

Use two coats of highly cut varnish for priming. To cut the varnish add mineral spirits to the varnish in the proportion indicated. Use a cone strainer (right) to strain any impurities out of both the varnish and the spirits.

You may need to gently mix the two substances together once they've been strained into the mix pot, but do so very slowly and carefully so as not to introduce air bubbles.

Sanding

Sanding roughs up the varnish enough for the next varnish coat to stick and so is done before each coat of varnish is applied, after the previous one has thoroughly cured. You don't need to sand after primer coats because they're not slick. Light sanding just roughs up the surface a bit and heavy sanding leaves the whole surface white and powdery. Heavy sanding is only done after there has been sufficient build-up of varnish that there is no danger of going through to the wood. Use 220 grit sandpaper generally, but 320 once you start to build-up thickness. After sanding wipe down the wood to remove the obvious dust. Chamois is good for this or any non-shedding non-linting cloth. Cloth diapers work, or the big bags of cloths you find for automotive polishing or in woodworking shops. If you're working outside you can can also wash down the item as long as there's time for it to dry before you need to varnish. You will still need to rub it down with a dry cloth before varnishing, but there won't be as much to remove.

I highly recommend the "Tri-X" paper. It's more expensive but it really can be used 2-4 times longer than regular sandpaper without building caking up with varnish dust and becoming unusable.

Varnishing – general rules and methods

1. Use gloves. Latex or nytrile or any kind of thin disposable gloves. You will protect your work from the oil on your fingers and your fingers from toxins. Hardware stores, marine stores, drug stores, art supply... buy 'em cheap in bulk.
2. Always strain the varnish through a cone strainer into a disposable varnish pot. I find that small paper cups work well for small jobs, and you can buy disposable paint pots (use the small ones) at the hardware store for larger jobs.
3. Always close the varnish can immediately after pouring into the varnish pot. Close it tightly being careful not to splatter as the excess in the rim is squeezed out. You may want to turn the can upside down between sessions. This puts the air / varnish interface, which will tends to thicken, on the bottom of the can. Later when you turn the can over and re-use it the top will be in good condition.
4. Just before starting to varnish use a tack cloth to lightly pick up any dust on the surface. If varnishing outside you should tack whatever you can do in the next 5 or 10 minutes to remove airborne dust. Leave the tack cloth at the end of the tacked section so you don’t forget to continue tacking when you’ve finished varnishing the tacked section.

5. Use high quality foam brushes sized appropriately to the size of the surface – 1” to 4” wide with 1” and 2” being the most commonly used. Do not try to re-use these to save money. The high quality brushes are sold in better paint stores – buy in bulk to save money. Cheap foam brushes are glued to paper around the wooden handle – poke up inside the brush to see if it’s paper or plastic. Only buy the ones with the plastic structure underneath. Some people use expensive varnish brushes - but then you have to clean them each day- and dispose of the dirty mineral spirits.
6. Varnishing requires good dry weather that’s not too hot. You also don’t want to varnish in direct sun unless it’s quite cool. Mornings are best, but make sure to wipe off any dew before beginning.
7. Varnishing is more like oiling than painting – you’re just spreading the fluid in a thin layer, not trying to push it into the surface like you do with painting. Imagine the brush is a feather… Likewise the brush needs very little varnish to do its job.
   1. Just dip the tip of the brush into the varnish. If the varnish drips as you move the brush – you have way too much on the brush. If the brush drags across the surface you either have too little on the brush or you have just varnished over tacky just-drying varnish. Avoid this – it makes ugly stripes.
   2. Sometimes you’ll see tiny tiny bubbles as you varnish – it seems to happen more in warm weather. Brush these out gently, but don’t worry too much. The tiny bubbles seem to take care of themselves – they’ll have disappeared when you come back the next day to sand.
8. There are two ways to apply varnish – in “plaid” and "with-the-grain". Plaid is used on the early coats to get good coverage; with-the-grain is used on later coats to get the best finish.
   1. To apply plaid: apply the varnish in two to three stripes across the grain, then brush with the grain across your new varnish stripes from dry-to-wet to create a smooth seamless finish. This brushing first in one direction and then across gives plaid its name. The number of stripes you can apply before brushing out depends on the thickness of the varnish, the heat of the day, your own speed and comfort level. If the varnish is at all tacky when you go to brush it out, cut the number of stripes until the brushing out happens with no tackiness at all.
   2. When you apply with-the-grain you don’t do much brushing out – just a few feathery swipes to cover holidays, smooth out excess varnish or catch sags before they happen. Always brush into the wet varnish – you do a sort of lifting of the brush before you get to the tacky parts brushed out in the last section.
9. You can use reflection from the surface to check for dull spots that indicate “holidays” or missed bits. This is easier after there are enough coats to create a shine. If the varnish is not tacky you can brush over these. If it is tacky just ignore it – you’ll pick that spot up on the next coat. Better a holiday (blank spot) than a sag (which should be sanded out after it's dry).
10. Done varnishing for the day? Throw away your disposable varnish paint pot - or let it dry out then dispose of. DO NOT try to pour what's left back into the can - you're just introducing gunk into your clean varnish.

enjoy your work...