Polyurethane resin, Alkyd resin, Phenolic resins

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Forum topic by Steven H posted 05-15-2011 08:34 PM 14642 views 0 times favorited 18 replies Add to Favorites Watch
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Steven H

1117 posts in 3233 days

05-15-2011 08:34 PM

Varnish is made by mixing and heating a resin (could be alkyd, phenolic or urethane or combination) and a drying oil (typically linseed oil, soya oil or sometimes tung oil) until the two become a new compound called “varnish”.

Polyurethane (also known as Urethane)

Urethane resin is very inexpensive produce than the others, making it lowesr price resin for the manufactor. It’s somewhat greater scratch resistance and heat resistance. This varnish is the most durable than other two, however it is not hard. Its a choice for children’s furniture, kitchen tables, and other subject to having abuse across the surface. It has taken over the varnish market. Polyuerthane is common found at home centers.


Alkyd resin is used to make lacquer and oil-based paint. The primary attribute of alkyd resin is its superior clarity. Makes it an excellent choice, when combined with soya oil, as a finish for fine furniture. Alkyd resin varnish made from soya oil produces a very warm, clear finish that is quite color stable over time. Manufactor add some Allkyd resin to polyurethane to reduce it from yellowing.

Phenolic Resin

Spar Varnish is same thing Marine Varnish.

It is commonly found in Marine stores. Spar Varnish is cooked with higher percentage of oil than Resin. The reason is because it is to let it to be flexible and soft in the sun. NOT ALL Spar Varnish are created equal. The Spar Varnish sold at home cetner like Minwax are not as good as you think. From What I known it contains poluyurethane and and UV inhibitors. This is a poor choice for exterior. While many of these products contain UV inhibitors, the better marine varnishes do not. They rely instead on the highly reflective nature of the finish film to deflect the damaging rays of the sun. This property places a much higher premium on regular maintenance to maintain the finish. However all finish do not last out door, so they need regualr maintanence.

A high quality Spar varnish can cost around $40-50.

18 replies so far

View hObOmOnk's profile


1381 posts in 4300 days

#1 posted 05-15-2011 09:43 PM

What about all the other resins used in making varnishes?

Just curious…

-- 温故知新

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Steven H

1117 posts in 3233 days

#2 posted 05-16-2011 05:16 PM

What do you mean?

There is Phenolic Varnish, Polyurethane Varnish, then theres Soya Alkyd Varnish.

View Sorethumbs's profile


38 posts in 2820 days

#3 posted 05-17-2011 04:56 PM

I think this line really needs some editing:

”Howeever all finish do not last out door, so they need daily maintanence.”

Daily? , really?

View Bill White's profile

Bill White

5101 posts in 4133 days

#4 posted 05-17-2011 05:27 PM

Uh? What’s your point?


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Steven H

1117 posts in 3233 days

#5 posted 05-17-2011 11:12 PM

hobomonk wanted know the difference between varnishes

View JJohnston's profile


1622 posts in 3464 days

#6 posted 05-18-2011 04:02 AM

What about them, hobomonk?

Just curious….

-- "A man may conduct himself well in both adversity and good fortune, but if you want to test his character, give him power." - Abraham Lincoln

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1334 posts in 3503 days

#7 posted 05-18-2011 04:17 AM

Hey Steven ~ I have been messing around with the Poly-acrylic casting resins (which can be used as a finish but are better suited to casting). They are pretty interesting in that they dry almost crystal clear when compared to the epoxy resins. Also, they are much thinner which allows the air bubbles to escape. I haven’t tried spraying the acrylic as a finish yet, but it is just a matter of time.

-- I just got done cutting three boards and all four of them were too short. (true story)

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Steven H

1117 posts in 3233 days

#8 posted 05-18-2011 06:08 PM

I have used Minwax Polyacrylic , General Finish Enduro Poly Topcoat, and Varathane Diamond Polyurethane. I have sprayed General Eduro Topcoat and it came out nice. Minwax Polyarcylic I only have brushed , its okay. I find that Varathane and General is better than Minwax. I haven’t used General Finish version Polyarcylic yet.

View hObOmOnk's profile


1381 posts in 4300 days

#9 posted 05-19-2011 03:30 AM

Note the spelling.
This product is actually a waterborne polyurethane enriched product. So says the chemists at Minwax. However, they don’t reveal the entire contents or formulation

Acrylics can also be used to enhanced alkyds.

Alkyds can be derived from more than soya oil. Originally, soya oil wasn’t used to produce alkyds.

Polyurethane isn’t typically used as a single resin in oil-based varnishes. It is used to enhance alkyd resins. Polyurethane products can vary greatly and different brands can’t be assumed to be all the same.

There are many other natural and synthetic resins used in modern and traditional varnishes.
I personally use copal enhanced varnishes, among others.

Too busy studying for my ordination to give more info at this time…


-- 温故知新

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Steven H

1117 posts in 3233 days

#10 posted 05-19-2011 07:37 AM

Im having hard time finding Minwax Msds product sheet.
You are right, not all products are made equal.

Waterboirne products labeled “polyurethane”, “Varnish” “Lacquer” is misleading . First of all, polyurethane is varnish made with urethane resin which is a reactive finish. Lacquer which is Evaporate finish. Waterboune finish is a coalesced finish.There is two types of waterbourne coating.

Arcylic and Arcylic/Polyurethane

View hObOmOnk's profile


1381 posts in 4300 days

#11 posted 05-19-2011 10:56 AM

MSDS are available for all Minwax products.

An MSDS (Material Safety Data Sheet) does not have to reveal the exact formulation of a product. It is intended as a safe handling notification document for the workplace, not necessarily for consumers.

MSDS is particular to the USA. Other countries may have different type of required documents.


-- 温故知新

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Steven H

1117 posts in 3233 days

#12 posted 05-19-2011 04:57 PM

I couldnt find the MSDS on Minwax website, so I went to rockler
Yes, I know it doesn’t show all ingredients but gives at least some clues :)

So what is the difference between these three varnishes?

Dammar varnish
Copal varnish
mastic varnish

View hObOmOnk's profile


1381 posts in 4300 days

#13 posted 05-20-2011 09:27 PM

”So what is the difference between these three varnishes?

Dammar varnish
Copal varnish
mastic varnish”

These are the names of natural resins that might be used in the making of various kinds of varnishes. They can’t be compared unless we know the exact contents of all the ingredients. These resins may be cooked with drying oils (e.g. linseed, tung, etc.), dissolved in organic solvents (e.g. turpentine) or dissolved in alcohol.

A simple form of damar resin varnish is just the resin dissolved in refined turpentine. It can be found in art supply stores.

Copal needs further clarification. There are at least two distinct types; one that is dissolved in turp and/or cooked with oils, and another type that is soluble in alcohol – aka Manila Copal. There is copal that is mined from archaic deposits and fresh copal (Manila Copal) that is collected from trees.

I use a lot of Manila Copal, blended with shellac and dissolved in alcohol, in my studio. We refer to the alcohol based varnishes as Spirit Varnishes. Sometimes I’ll add natural pigments to make “Shellac Paint”.

Here’s a picture of some of the test finishes where I used my Copal/Shellac Varnishes with Pigments.

-- 温故知新

View Bob123's profile


6 posts in 2697 days

#14 posted 06-28-2011 06:54 PM

Hello Hobomonk,

What type(s) of varnish might have been used between 1900 and 1910 on mission furniture? I know a great deal of experimentation was done then with stains; and both wiping varnish and shellac were used over the stains. Tried and True wiping varnish says it uses an 1880 recipe but I was told it’s not as durable as the varnishes used around 1900 on mission furniture.

What I’m looking for are recipes for period varnishes using either traditional or modern ingredients, and is more durable than Tried and True varnish. One concern I have with currently available products is I’ve been told they are going to be phased out over the next ten years to reduce VOCs, according to an employee at WoodCraft. If I have to make my own varnish in the future I’d like to know how.


View hObOmOnk's profile


1381 posts in 4300 days

#15 posted 06-28-2011 08:37 PM

Oi-based cooked varnishes of that era usually used linseed oil and natural resins, such as copal, asphaltum, colophony (rosin) and other resins. I occasionally cook my own varnishes, but it’s a real PITA.

Spirit varnishes of that era used alcohol-soluble resins including shellac, Manilla copal, mastic and others. I mainly use spirit varnishes at this time because they meet my needs.

Here’s a recently released book on 19th woodworking finishes that you might find useful: Shellac, Linseed Oil & Paint. The author is very accurate in both his chemistry and period correctness.

-- 温故知新

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