LumberJocks

I know nothing about finishes

  • Advertise with us

« back to Finishing forum

Forum topic by BJODay posted 10-01-2015 11:49 PM 888 views 0 times favorited 11 replies Add to Favorites Watch
View BJODay's profile

BJODay

514 posts in 1409 days


10-01-2015 11:49 PM

Could someone give me a quick rundown on different types of finishes?

I usually use water based poly varnish. It holds up okay if away from sunlight and water. Otherwise I’ve used oil based varnishes but I hate applying them. I don’t have the room, (or cash), to set up a spray booth.

What is lacquer?
What is different between lacquer and varnish?
What is Shellac?
Are there advantages/disadvantages to these finishes?
I’ve seen aerosol versions of both shellac and lacquer, (not to be used indoors I would assume).
Are there other options out there?

Thanks for any help.
BJ


11 replies so far

View Fred Hargis's profile

Fred Hargis

3947 posts in 1959 days


#1 posted 10-02-2015 11:53 AM

Here’s my cliff notes: Lacquer is made with cotton or a cellulose dissolved in nitric acid for the resin (hence the name “nitro celllose”) diluted with a real witches brew of solvents, that’s what makes it so flammable it’s fairly dangerous to use. Varnish, on the other hand, is a compound of resins and a drying oil cooked together until they form varnish. Typical resins are urethane, alkyd (my favorite), and phenolic. The drying oils can be linseed oil, tung oil, and soya oil (again, my favorite) among others. In common usage, when most people say “poly” they are referring to varnish….the urethane resin formulas. However, due to the magic of Norm and other factors many manufacturer’s have siezed upon that word “poly” as a magic marketing ingredient and by adding just a dollop of urethane to everything, they can label the damn stuff “poly”, and we dutifully call it that. Point being, when someone says “poly’, it pays to ask exactly what they refer too. Shellac is a secretion of the lac bug, gathered mostly in India (I think) and then refined to the various grades and colors you see offered. Mostly sold in flakes to be dissolved in DNA, Zinnser offers some canned versions that have a magic ingredient to make it keep a little longer. Generally, shellac mixed from flakes has a shelf life of less than one year, and often closer to 6 months. Undissolved flakes keep a very long time when properly stored. Most waterborne finishes (commonly called “water-based”) are actually acrylic finishes though some are called “lacquer”, or “polyurethane” and other stuff as far as I know. Waterbornes have come a long way in terms of durability and rapidly becoming the only one many of us can get.

Differences are many, but quickly shellac and lacquer (the real stuff) are evaporative finishes, that is, they dry by letting the solvents evaporate and then the resins harden. Typically, the can be re-dissolved by putting the proper solvent on them. They tend to be a less durable and water resistant than the alternatives. Varnish cures by reacting to oxygen. The solvents (typically mineral spitits) evaporate, then the resins cure by reacting with O2..and it takes time, which is why the dry times are so long. The molecules go through a cross linking process while curing and form a very tough and durable finish. Waterbornes have a solvent (usually glycol ether) and water. The water simply holds the molecules apart during application. While drying, the water evaporates allowing the glycol to soften the surface of the resin which becomes sticky…they then link and form a finish. If they were truly “water based”, putting water on them would re dissolve the finish; but that’s not the case. Once cured they form a fairly durable coating.

There are other choices, catalyzed and conversion formulas used in industry are much more durable than anything we mortals can use..but I have a suggestion: buy a copy of Bob Flexner's book and read it….it’s not at all boring and reads much like a novel. Jeff Jewitt's the same info, but is organized a little differently. If you buy Flexner’s book be sure to get the updated edition.

-- Our village hasn't lost it's idiot, he was elected to congress.

View BJODay's profile

BJODay

514 posts in 1409 days


#2 posted 10-02-2015 01:58 PM

Fred,
Thanks for the information. I have gotten used to using water based varnishes. I like the fast dry times and I usually apply thin coats with a rag.

I have a project coming up this winter. I’m going to attempt to build a mandolin. Water based varnish won’t hold up for this. I’ll pick up the book and do some homework before I’m ready to finish.

Thanks again
BJ

View Bill White's profile

Bill White

4456 posts in 3426 days


#3 posted 10-02-2015 01:59 PM

Fred, that was the most user friendly explanation on a topic so complex and full of chemistry unknown to the layman.
Well done Sir.
Bill

-- bill@magraphics.us

View CB_Cohick's profile

CB_Cohick

460 posts in 717 days


#4 posted 10-02-2015 02:03 PM

I have been told, not sure if it is truth or not, that shellac is derived from the shell of the lac bug. I wonder if crickets would work …

-- Chris - Would work, but I'm too busy reading about woodwork.

View jmartel's profile

jmartel

6575 posts in 1616 days


#5 posted 10-02-2015 02:47 PM

Not the shell, but a secretion that the bugs make, CB.

BJODay, pick up a copy of Bob Flexner’s Understanding Wood Finishing book. All you need to know is in there.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

View Holbs's profile

Holbs

1378 posts in 1495 days


#6 posted 10-02-2015 02:56 PM

Thanks for the detail info, Fred. “Finishing” is something I have not yet tackled, and I admit a little intimidated by. I’ll purchase that Bob Flexner book to help alleviate the fog of confusion

-- Yes, my profile picture is of a Carpenter Bee! The name is derived from the Ancient Greek "wood-cutter"

View Wildwood's profile

Wildwood

1886 posts in 1601 days


#7 posted 10-02-2015 07:09 PM

Here is a nice overview on finishes by Jeff Jewitt.

http://www.finewoodworking.com/toolguide/articles/selecting-a-finish.aspx

Bought Understanding Wood Finishing by Bob Flexner many years ago and still refer back to it often. Flexner & Jewitt write a lot of articles and available online. Both have written books easy to understand and will save you time and money finishing wood.

Wood Finishes
http://www.amazon.com/Great-Wood-Finishes-Jeff-Jewitt/dp/1561582883/ref=asap_bc?ie=UTF8

Wood Finishes 101, by Flexner
http://www.amazon.com/Wood-Finishing-101-Step-Step/dp/1440308454/ref=pd_bxgy_14_img_3?ie=UTF8&refRID=1PYVVVSPQ6MHSGHHNT7Q

-- Bill

View Hammerthumb's profile

Hammerthumb

2533 posts in 1441 days


#8 posted 10-02-2015 07:50 PM

I have to agree that Fred’s explanation of the different finishes is one the best I have ever read. I cannot disagree with any of bit of that information. Well done Fred!

-- Paul, Las Vegas

View AandCstyle's profile

AandCstyle

2575 posts in 1723 days


#9 posted 10-03-2015 12:22 AM

Hey, BJ, you might benefit from looking at stewmac.com and targetcoatings.com. Both have info specific to finishing musical instruments. I have been using Target’s EM6000 for years and am very happy with the results I get. I spray it, but it can be applied with a brush as well. Search the finishers forum for more info if you are interested. HTH

-- Art

View BJODay's profile

BJODay

514 posts in 1409 days


#10 posted 10-03-2015 04:38 PM

Thanks Art, I check it out.
BJ

View BJODay's profile

BJODay

514 posts in 1409 days


#11 posted 10-05-2015 01:12 AM

I picked up Bob Flexner’s “Understanding Wood Finishing” this weekend. Just the chapter on oils made the purchase worthwhile. I’m recognizing many errors I’ve made while finishing previous projects. Many were due to my impatience. Always room to improve.
BJ

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com