Wood Finishing Basics
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rncx



Joined: 21 Jun 2008
Posts: 660
Location: Little Rock, AR

PostPosted: Sun Apr 25, 2010 3:44 am    Post subject: Wood Finishing Basics Reply with quote

kinda applies here too, this idea struck me on another forum i visit...

Quote:
in the past month on this forum, there have been 7, by my count, threads where someone had a failure with a particular finish.

one was due to funky wood grain, one was due to a wood species that doesn't stain well. those are not even finish problem threads, really, more like wood problem threads.

the other 5 were problems with polyurethane varnishes. adhesion problems, bubbling problems, mixing problems (albeit some mixed with incompatible things).

polyurethane is so heavily marketed and readily available because it's CHEAP. plastic urethane resins are cheaper than other resins, much like the plastic parts on harbor freight tools are cheaper. do people insist on only having plastic tools in their shops, decrying any alternative that is not plastic because the plastic store says plastic is better? no. so why spend all the money on the tools, and all the money on the lumber, and all the time to build something, only to say "screw it, the plastic goo in a can from home depot is good enough".

we should have a sticky thread (pun intended), that answers basic finishing questions like...

is polyurethane varnish good for ...?

1) no
2) floor? arguably
3) (anything else i can think of, see #1)

there are lots of other options than plastic goop over minwax stains and filler, folks. unfortunately, not on every street corner, they have those locked up. looks like if you go to woodcraft they have that locked up too, under the woodcraft varnish section on their website, there are 5 variations of polyurethane and behlen's rock hard, that's it .

but there is more out there, you just have to order it online or go to specialty shops.

my list of alternatives off the top of my head...

1) waterlox (waterlox.com) tung oil based resin varnish, also an alternative for floors. a trained monkey can apply this stuff smooth and even with a brush, it's about as dummy proof as it gets.
2) allback paints (solventfreepaint.com) they make linseed oil based stains/varnishes, as well as linseed oil based paint (similar to what lead paints used to be made out of), they also sell natural pine tar, which is a good exterior stain/water sealer as well.
3) tried and true varnishes (triedandtruewoodfinish.com), they also make linseed oil/natural resin varnishes.
4) i don't use them personally due to a preference for oil, but target coatings (targetcoatings.com/shop/) specialize in water borne lacquers and varnishes
5) do you know there are lots of colors of shellac? most people don't, probably, since the only thing home depot carries is amber or clear in the zinnser cans. but check shellac.net and shellacshack.com, there are actually lots of colors that most folks have probably never seen (or have seen, on an old piece of furniture, and wondered how they got brown shellac on something when brown shellac isn't available...it is! just not in a zinnser can).

not really a varnish, but..

6) while you can't get lead paint anymore, do people know that you can still get milk paint? milkpaint.com and realmilkpaint.com are two sources i know of. if you need to paint the deck or fence white (or the whole house white, for that matter), this stuff will last longer than any paint you can get at a hardware store, and you don't have to worry with priming, just add water to it, stir it up, and go. similar to the the traditional 'whitewash' that people used on fences in the old days.

many of the above have been used for at least hundreds, if not thousands, of years.

try them! you might find something you like. as of now we have to scour the internet for alternatives to minwax stains and polyurethane, and alternatives to acrylic or alkyd paint. if no one scours the internet to buy and try such things, one of these days minwax stain, minwax polyurethane, and deft spray-bomb lacquer will be all that there is no matter where you look. no matter which alternative you use, one thing is guaranteed, you won't be the one making one of those "help my poly bubbled up" threads .


in addition to the above, for old floors (the most common refinishing scenario that comes up), the new method of oil stain + polyurethane is about the worst possible method i can think of to refinish an old floor. for one, if you don't like the color that the stain ends up being, you're screwed. as soon as that stain touches that old wood, that old wood is going to readily drink it as fast as possible. you'll have to chemically remove the stain or sand it all bare again if it isn't what you want. two, polyurethane varnishes NOTORIOUSLY do not stick to waxy old finishes, like the waxed shellac that was probably originally on a 100+ year old floor. if any of the old finish remains it will bubble up, it will not stick, and guess what, you'll end up putting a chemical stripper on that too to get rid of it.

so do yourself a favor, skip the minwax aisle at home depot. they're more trouble than they're worth.

figure out what they used originally and use it again, after all it lasted over 100 years, right? it's still available, you just have to look for it on google, rather than at the big box hardware stores.


Last edited by rncx on Sun Apr 25, 2010 4:48 pm; edited 1 time in total
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jade



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PostPosted: Sun Apr 25, 2010 7:59 am    Post subject: Reply with quote

EXCELLENT!

thanks.....
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johnleeke
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PostPosted: Sun Apr 25, 2010 9:50 am    Post subject: Reply with quote

I agree. I've retitled this "Wood Finishing Basics" and made it "sticky" so it will stay at the top of the list.
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Last edited by johnleeke on Sun Apr 25, 2010 2:39 pm; edited 1 time in total
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rncx



Joined: 21 Jun 2008
Posts: 660
Location: Little Rock, AR

PostPosted: Sun Apr 25, 2010 2:00 pm    Post subject: Reply with quote

so to expand, the basic differences in various wood finishes...

varnish: usually borne with an oil, a transparent wood finish. these days there are water borne alternatives in some varieties. 3 parts: thinner, resin, and a drying oil.

lacquer: in modern terms, a type of varnish designed to dry faster than oil varnishes, and be very hard and durable once cured. not as flexible as an oil varnish. for our purposes, primarily for furniture.

stain: a penetrating colorant. usually oil borne.

dye: a colorant sold in concentrated form to be mixed with other finishes or solvents, can be applied in a number of ways (spray, brush, wipe).

filler: in commercial form, a substance of wood fibers and a solvent that is designed to fill voids in a surface to be finished, whether those voids be nail holes or natural patterns in the grain of the wood. shellac can also do this.

sealer: a substance whose purpose is to be absorbed into the wood and inhibit the wood from absorbing other finishes.

wax: typically, common paste wax. an alternative top coat that you would apply and buff away just like waxing a car. very protective against water, just like car wax is.


Last edited by rncx on Sun Apr 25, 2010 4:41 pm; edited 1 time in total
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rncx



Joined: 21 Jun 2008
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Location: Little Rock, AR

PostPosted: Sun Apr 25, 2010 3:53 pm    Post subject: Reply with quote

"so with all of these available, which is compatible with which, what can be used for what (filling, sealing, top coat)?"

lacquers, and specifically shellac, is the only thing that can effectively replace all other finishes and finishing products. that's why it's still so widely available, it can't be replaced. it sticks to anything. therefore it's useful as a barrier between incompatible finishes. it can be used as a grain filler, by applying multiple thinned coats to bare wood and sanding. it can also be used as a top coat, it leaves a high gloss surface that can be buffed smooth. it's also an effective sealer, since only alcohol will cut it, so it's an effective barrier against oil borne finishes and stains. it can also be melted into nail holes and other imperfections to act as a solid filler. the only caveat is it can't be used outside, since sunlight will melt it.

as for the others, as mentioned above lacquers are primarily designed for furniture top coats. they are hard and non-flexible films when they cure,

varnishes typically denote penerating oils. penetrating in that they are supposed to sink deeply into the wood and act as a barrier to water as well as a finish. they remain more flexible than lacquers do. if you prefer a darker more visible grain in your finished result, oil varnishes can also be used as a sealer. oil varnishes are also good top coats, and easy to apply since they dry slowly, and therefore will level themselves as they cure, leaving a fairly smooth finish with no extra effort on your part.

"why stains and dyes, what's the difference?"

in formulation, not much difference. in application, alot of difference. staining a wooden piece with an oil stain somewhat of an 'all or nothing' approach. once that stain is applied, the wood is drinking it. and it won't easily come back out. that color is for all intents and purposes, permanent. this is good in some ways, not so much in others. good in that small surface dents and dings will not show, even if they reach the bare wood, because the color is below that surface. bad in that if there is any other substance there besides the wood itself, such as a filler or glue residue, it will not absorb the stain like the wood will, and will not blend in. i'm sure everyone has tried the good ole minwax 'stainable' wood filler to find that it's not really stainable at all, and will never be uniform with the wood around it. that's a problem not easily overcome with penetrating stains. some species of wood also do not absorb stains evenly (like pine, and maple), that's also a problem not easily solved, since there's no effective way to test the board before applying the stain to it, and then it's too late.

dyes on the other hand are more like semi-transparent paint. they are applied on the surface of the wood, rather than applied with the intent of the wood soaking it all up. they add color as evenly as you can apply them. most professional finishers will spray the dye, to allow for even application in a short period of time, and very even coverage. they can be wiped and brushed, however, with a little practice. since the color is a surface film with a dye, the dye will effectively cover fillers and glue residue and other such things evenly.

"so if shellac can do all of the above, why don't i just use shellac for everything?"

there is no reason why, you can use shellac for everything. it's also cheaper than alot of other options. hence the statement 'skip the minwax aisle'. if your surface preparation is meticulous, and you know precisely what you're doing, you can apply the method of oil stain + a topcoat with success, and wind up with a good finish. but if you don't, you'll probably be less than pleased with the result. if you do know precisely what you're doing, you'll probably arrive at the conclusion that there are easier ways with more margin for error. that's realization i have arrived at over the years. i've built a house full of doors and windows and cabinets, and refinished my old and badly stained by a previous owner floors. i have never used a penetrating stain on any of it. it's simply too risky. shellac + an oil varnish replaces the staining steps and will always wind up giving me a uniform color, regardless of the wood species and regardless of that species' propensity for absorbing (or not absorbing) a finish.

"so what are the basic steps to finishing that should always be followed?"

1) sanding.

the benefits vary by wood species, but generally, start with a rough grit (80 to 120) to remove dents, dings, and large imperfections, proceed up to 160 to 180, and then finish with 220 to smooth the surface to its final sheen. some species of wood benefit from proceeding up through 300 and 400 grits, with some this can do more harm than good (specifically on species that don't react well to heat, for example, yellow pines). you always sand with the grain, never against. if you prefer to use a power sander, random orbital sanders are generally the only sanders that work well enough for fine finishing work. the circular motion that they use when applied to the surface cleans up any cross-grain motion. other vibrating sanders can work against the grain since they're bound to the motion of your hand. so if you buy one power sander, make it a random orbital one.

2) sealing and grain filling.

some species (such as red oak, walnut for example) have open pores in the wood. if you want to achieve a mirror smooth finish, those pores must be sealed. there are products specifically advertised as grain sealers, but honestly none perform better than super blonde shellac from my experience. note that super blonde is not available in the zinnser cans at home depot, you'll have to order it from a shellac supplier. the difference with super blonde is it is almost perfectly clear. it has no color at all. the idea is, you use 1 pound of super blonde shellac flakes in a gallon of alcohol, to make a thin very clear finish. you apply 3 or 4 coats of it to your bare wood, and then sand it after the shellac coats are dry with a flat sanding block (sandpaper wrapped around a flat board in your hand). this process usually needs to be done twice to achieve a satisfactory result. the shellac will remain in the voids and pores of the wood, leaving you with a very smooth and flat surface. after your color coat(s) are applied, you will be left with a uniform surface, and the wood's pores and voids will not be felt in your final finish. when the pores are filled, you add one more even coat of your 1 pound shellac as a sealer coat, applying it as evenly as possible. alternatively you can use an oil varnish as a sealer to make the grain a bit darker. that's personal preference, one has no benefit over the other other than appearance.

a more thorough writeup on the process of doing this is here.

3) color (optional).

if you wish to color the wood something other than its natural color, this is the point at which you apply the color coat. the wiping of a penetrating oil stain will work at this point, but be absolutely sure the results are what you want by testing on a scrap piece. if it isn't, you have no choice but to remove everything and start over. if you choose to use a dye at this point, you'll also need to mix and test that on something other than the final piece to get what you're looking for. dyes can be applied by hand, but the process is much easier to perfect by spraying, and that of course requires some sort of spray equipment. there are inexpensive turbine powered spray units available (i personally use an earlex 5000, available at woodcraft, for about 300 dollars) that do not require an air compressor, but there is a disposable solution as well. any hardware store with an automotive department should have a spray system from a company called preval. it's in effect, a disposable aerosol can. you attach a cup to the bottom of the can, and the can sprays whatever is in the cup, then you throw it away when the canned air is gone, and use another one. they sell for 4 or 5 dollars each. these are a great alternative for spraying stains and dyes if you don't have a proper spray gun + turbine or compressor.

a good discussion on spraying dyes is here.

alternatively, without spray equipment you can use colored shellac in lieu of the stain or dye. this is the easiest solution, since it requires no spraying at all (although shellac can be sprayed, if you prefer, and it's easier to apply evenly that way). there are many colors of shellac that are naturally available, mostly shades of red to brown. if you require a different color, dyes are soluble in alcohol, and therefore, will mix just fine with shellac. thus, the color options of shellac are infinitely adjustable.

4) top coat.

if you used shellac for color, and are satisfied with how evenly the shellac coat came out, you can just quit at this point and call it done. a coat of wax will help protect the shellac from damage, but it's fine as a top coat itself. you can apply varnishes and lacquers on top of shellac (or the dye/stain) if you prefer. personally, i do use oil varnishes at this point, for the purposes of ease of use. a big difference as mentioned above, between oil varnishes and lacquers/shellac is that they dry very slowly, and will therefore level themselves, requiring little or no buffing to smoothness after they are cured. so they are perfectly suited as a topcoat for shellac. you can apply the shellac for color, then buff the shellac (i use steel wool, real steel wool will work as long as you don't use a water based top coat, if you do the water will rust the steel residue and leave rust marks in your finish, so if you plan to use a water based top coat, use imitation steel wool, which is similar to a brillo pad), then apply an oil varnish on top of the shellac. the varnish will hide any imperfections in the shellac, as long as the varnish and the shellac are similar in color, and leave you with a relatively smooth finish without any further effort. for things like moldings and floors, this is 'good enough' for lack of a better word. if you intend to buff/polish the top coat, add one more coat to whatever number of coats you planned to use. you need something to remove, to polish, in short.

5) buffing/polishing

if this is a piece of furniture, that you desire a more even and consistent surface on than you would expect on a floor or baseboard, the last step is to buff it smooth. unfortunately the first step in that is...wait. don't touch it. your previous coat of finish has to be fully cured before you can buff and polish it. polishing a finish is nothing more than sanding it, with very high grit abrasives, so to do that it has to be fully cured. different finishes cure in different time frames, but generally two weeks is sufficient for anything you might use, other than a slow drying oil varnish, in which case i'd give it a month. back to your random orbital sander, and wet sand paper in the desired grit range. generally, we're talking about satin, semi-gloss, or high gloss as the three desired sheen levels. first, use the sheen you desire in the initial top coat. if you want to wind up with satin, use a satin finish as your top coat (if you use shellac as a top coat, there is an additive you can order from shellac suppliers to dull it to a satin sheen). if you desire a high gloss, use high gloss. thus any small voids that may be present in the finish will have the sheen you wind up with by default. for polishing purposes, you want to lubricate the surface (water and a little dish soap work fine) and sand with your orbital sander in the grit range that will give you the desired sheen. for satin, 600-1000. for semi-gloss, 1200-1500. for high gloss, 2000-4000. you're not trying to remove much finish, just even it. this is difficult to explain without pictures, but trying it under a bright light will show the effect, and a little trial and error will show the results. the only thing to note is to be very careful on edges. it's easy to blow through the entire finish and accidentally knock edges down to bare wood. so tread very lightly on those.

that's the basic process, that will work with any finish regardless of its formulation.

a note on brushing, in the next post...
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rncx



Joined: 21 Jun 2008
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Location: Little Rock, AR

PostPosted: Sun Apr 25, 2010 4:13 pm    Post subject: Reply with quote

while spraying finishes is much easier than wiping or brushing, and much faster, any finish can be brushed. think about it, they didn't have spray guns before the invention of machine controlled compressed air, yet everyone has seen centuries old pieces with immaculate finishes.

any finish can be brushed or wiped. it takes more effort, and a little more hand skill, but it's not rocket science.

with any brushed finish, whether it be paint, clear, or whatever, most people i've seen using paintbrushes do not grasp the basic technique and understanding of how a brush works.

with transparent wood finishes, bad technique is multiplied many times over, since subtle light variations clearly show even the smallest finish imperfections.

so, how to paint with a brush. first, things that you don't do that i have seen people do lots of times..

1) do not dab it on
2) do not flood the surface and then spread the finish after
3) do not try to 'just get a little' finish on the brush to control the thickness of the finish itself

a brush is designed to hold a lot of finish, and dispense it in smaller amounts. so don't try to defeat the design of a paintbrush. it has worked the same way for thousands of years, you can't make it work differently ;).

a) saturate the brush with whatever thins the finish you're working with. alcohol in the case of shellac, mineral spirits in the case of oil varnishes, or lacquer thinner in the case of non-shellac lacquers, and shake out the excess. this will help the first bit of finish flow more evenly throughout the brush.

b) dip the brush deep into the finish, near the hilt of the brush. get it full, so that you minimize having to stop and go get more finish from the can. you don't control how much finish you get from the brush by how much finish is in the brush, the two have no relation to each other.

c) let the excess drip out, then tap the hilt on the edges of the can to force more out. in short, get rid of the drips. you should be left with a full brush at this point, and are ready to paint.

d) apply the finish with the brush with as little pressure as possible, just gliding the brush along. just overlap each stroke as you go across enough to keep a wet edge. don't overlap entire strokes (especially with fast drying lacquers and shellacs). always go with the grain of the wood, never against.

e) since edges and joints are prone to run more than flat surfaces, plan your brushing in such a way that you get to edges and joints when the brush is near empty. that way you can be a bit rougher with the brush at those spots without fear of runs.

if you brush properly, you'll find that any finish can be brushed, you just have to use the brush in the way it was designed to work.

and finally, don't use those foam things they sell at the hardware stores. if you use the brush properly you won't get many hints of brush strokes in the results. so don't try to eliminate brush strokes by using a bad paintbrush. i can't think of any purpose that those foam contraptions are good for (other than causing bubbles in your finish). use a real brush, and learn the technique, you'll get better results.

the same technique above applies to any sort of brushing, even finishing a floor. you do the same thing with a wool floor finishing mop that you do with a paintbrush. you saturate the mop head, press out the excess, and glide it along without any pressure, overlapping an inch or so to keep a wet edge. it's not difficult, it's one of those things that 'just works' as long as you use the tool the way it was designed to be used.
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Mike-in-Maine



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Location: Fort Kent, ME

PostPosted: Sun May 02, 2010 11:17 am    Post subject: Reply with quote

Excellent info here. Ive been refinishing (old) and finishing (new) pieces for about 10-11 years now. I can say without a doubt, I have never stopped learning. My complete level of ignorance was astounding when I started. That doesn't mean I was a fool or an idiot, but rather that there was so much I simply hadnt yet learned back then. To this day there is still so much I dont know, but Ive come a LONG way and my pieces show it.

After I complete a piece there always seems to be a 6 month period where I realize what I could have and should have done better. This hasnt changed in 10 years, although with each new project I incorporate the lessons learned from the previous "mistakes".

The biggest thing ive learned is that the best way to learn seems to be from experts (people!) who have WAY more experience than me. I've got ALOT of books on wood finishing, some very new and some very old, all are great reference sources, but not a single one of them "explains" to the level we really need, the intricacies and subtle nuances we need to create perfect finishes.

Thats been my primary problem. I read alot, take what I read and use it, then realize that they didnt discuss the problems with their instructions, in a literal sense. Happens every time. These days im very cautious with taking everything in a book as the end of the story. There is always something they overlook in the explaining of a technique.

RNCX's posts here are perhaps better than any book ive read regarding actual technique and the question of what to cover (or not) a shellac finish with. All the books I own (as i said, some of them are extremely well written) fail to address many of the things rncx has talked about. I've learned many of his lessons on my own by error, and some things he has discussed are things I suspected by could never (or never dared to) verify... a few things are things I simply never knew.

Thank YOU rncx!
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rncx



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PostPosted: Sun May 02, 2010 2:47 pm    Post subject: Reply with quote

i'm pretty much of the same opinion. building things is easy. finishing things requires a lot more experience. i wouldn't call myself a master finisher by any means, i think i'd describe my finishing skills as intermediate.

i work more on improving my spraying now than anything else, but i don't know that you ever truly gain proficiency with spraying, since there's so much variation between guns, finishes, etc. spraying shellac is about the easiest "quick and dirty" way of getting a decent finish on something with minimal effort, so for most things, that's the method i use, with a slow drying oil varnish on top to wind up with a fairly smooth and even finish without too much polishing.

either way, i think achieving a good finish on something whether it's new or old is alot more about the process than perfect technique. if you know the process, you can get very good results even without much experience. it's more about taking the time and knowing the process, than skill with a pad or brush.
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TimB



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PostPosted: Thu Dec 02, 2010 8:58 am    Post subject: Melting Shellac into nail holes Reply with quote

Could someone describe to me the process of melting shellac into nail holes as filler? I have some flake shellac on hand and would like to give this a try on some old pine boards.
Thanks

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rncx



Joined: 21 Jun 2008
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PostPosted: Thu Dec 02, 2010 11:17 am    Post subject: Reply with quote

i've seen it done back home in antique furniture repair shops but am by no means an expert in it, it does have a 'technique' to it that will take some trial and error.

generally you put a little wax around the area to be filled, and the wax will act as a barrier to the surrounding finish, only allowing the shellac to flow to that point.

the heat time is similar to solder as well, once it gets flowing it moves quick, and when the heat is removed it will dry quick.

the few pieces i tried it on i had better results by overbuilding the filled area and then polishing it back to smooth with an alcohol soaked rag, then wiping on a few more coats of the same color shellac to blend it.

a skilled hand could probably avoid all of that and fill the spot to be filled to a more level surface with the rest, though. it would just take practice to learn the technique.

a site with better detail of the process from a luthier...

http://www.frets.com/fretspages/luthier/Technique/Finish/StickShellac/sticklac1.html
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smithsash



Joined: 23 Jan 2010
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Location: providence, ri

PostPosted: Thu Dec 02, 2010 2:48 pm    Post subject: Stick Shellac Reply with quote

What you're looking for is called "stick shellac"

It is shellac formed into sticks maybe 1/4" x 1/2" x 6" and is available in a veritable rainbow of shades.

You need an alcohol lamp (or an electrically heated knife) and a burn-in knife. You heat the appropriate stick of shellac over the alcohol flame and drip the wax into the hole. You can then take the knife, heat it in the flame and use the hot blade to melt/smooth the shellac into the hole. Excess shellac can be "shaved-off" with a chisel and smoothed with alcohol.

It is commonly used in furniture restoration.

Check out this link

http://www.frets.com/fretspages/luthier/Technique/Finish/StickShellac/sticklac1.html


Good luck!

Justin Smith
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TimB



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PostPosted: Fri Dec 03, 2010 8:29 am    Post subject: Stick Shellac Reply with quote

Thank you both for the advice and helpful link. I will try to get my hands on some stick shellac and give it a shot.
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