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Can I slow down the drying of shellac?

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Forum topic by ohtimberwolf posted 05-18-2019 01:58 PM 516 views 0 times favorited 16 replies Add to Favorites Watch
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ohtimberwolf

931 posts in 2741 days


05-18-2019 01:58 PM

I want to apply Zinnsser Bulls Eye Amber shellac to a wooden door and the shellac dries rapidly. Is there a way to slow down the drying of shellac to prevent lap marks or shading? Can it be rolled on successfully? larry

-- Just a barn cat, now gone to cat heaven.


16 replies so far

View jdh122's profile

jdh122

1073 posts in 3207 days


#1 posted 05-18-2019 02:18 PM

The thinner the cut (ie the more alcohol there is relative to the amount of shellac), the slower it dries. Of course this means more coats are needed. So you can add denatured alcohol and it will dry more slowly.
I don’t know if there are more complicated ways to change drying time…

-- Jeremy, in the Acadian forests

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shipwright

8305 posts in 3187 days


#2 posted 05-18-2019 03:19 PM

For pre-mixed you are pretty much stuck. If you make your own from flakes you can use a slower alcohol (isopropanol) but alcohol based finishes are going to be fast.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View Dark_Lightning's profile

Dark_Lightning

3445 posts in 3498 days


#3 posted 05-18-2019 03:24 PM

I’d take it off the jamb spray it. I’ve never had what I consider a decent finish with amber shellac unless I sprayed it.

-- Random Orbital Nailer

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ohtimberwolf

931 posts in 2741 days


#4 posted 05-18-2019 03:35 PM

Thanks guys, unfortunately it didn’t work for me and I work fast. That being said, it was the inside of a mud room door so the experiment showed me what not to do. I didn’t know you could spray this stuff but it must be a booger to clean your equipment when you are finished. Any belated tips are still welcome. larry

-- Just a barn cat, now gone to cat heaven.

View Fred Hargis's profile

Fred Hargis

5545 posts in 2882 days


#5 posted 05-18-2019 03:42 PM

I have heard (but not tried) that putting a teaspoon of turpentine into a pint of shellac will slow it’s drying dramatically, you might try it and see if if it’s what you want. But cleaning spray equipment when using shellac couldn’t be easier. Skip the DNA for cleaning, use household ammonia. Ammonia absolutely destroys shellac, your gun is really clean. Just rinse it thoroughly with some warm water and your done. The only caution is that ammonia can stain aluminum (I guess, it did mine) although this dones no harm; it’s an appearance thing. I put some ammonia into a 5 gallon bucket with warm water and soak the parts I can, I also spray some of the ammonia mix through the gun to get the internals clean. Works great, and is a cheap way to do it.

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

View bondogaposis's profile

bondogaposis

5399 posts in 2740 days


#6 posted 05-18-2019 03:52 PM



I d take it off the jamb spray it. I ve never had what I consider a decent finish with amber shellac unless I sprayed it.

- Dark_Lightning

Yeah, me too, spraying is the only way to go with shellac.

-- Bondo Gaposis

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CaptainKlutz

1360 posts in 1883 days


#7 posted 05-19-2019 12:00 AM

Yes. Shellac can be made to dry slower.

Can slow down evaporation rate with any finishing material, by using a slow evaporation solvent that is compatible with system. There are many references on web with solvent evaporation rates and compatibility, such as:
https://www.eastman.com/Literature_Center/S/SOL030.pdf
https://www.eastman.com/Literature_Center/R/RES001.pdf (shellac is considered a rosin ester in this chart)

IMHO – Most common retarders for spraying lacquer and urethane systems are Methyl N-Amyl Ketone (MAK) or Propylene Glycol Monomethyl Ether Acetate (PGMEA or PM Acetate). Common retarder for water based systems is Propylene Glycol (not to be confused with PGMEA).

If you have ever dealt with automotive spray paints, they offer secret blends of retarder solvents designed to work in narrow range of temperature/humidity. The solvent blend is designed to slow evaporation, but may also use solvents to reduce runs/sags with slower evaporation, or fix other issues created with retarding the finish. It gets complicated quickly, but once you get educated on how different solvents work, you can easily make your own retarder. Regardless, back to shellac…

Since shellac is dissolved in alcohol, petroleum mineral solvents (or Stoddard solvents) just aren’t compatible. Compatible means it will mix with other solvent(s), not turn cloudy, and doesn’t impact finish final properties.
What is compatible?
If you read the MSDS from qt can of Zinseer on Amber Shellac you find they use 2-Propanol and Ethanol for main solvents. The MSDS for the spray version they add n-Butanol, and acetone. Which just proves that you can use more than alcohols (ketone’s) in shellac. :-) Most ketone and some ether/ester solvents are compatible with alcohols.

Here in AZ desert low humidity, have to use extra solvent plus fast retarder in winter, and slowest retarder in summer; otherwise normal fast evaporation finish might dry before it hits the surface. I mostly spray de-waxed shellac dissolved from flakes (used as blotch control), and use n-Butanol and/or PGMEA as retarder with 90/10 ethanol/methonal as main solvents.

The PGMEA has nasty odor which forces full respirator mask all time, but is compatible ester solvent. Should always use respirator when working with shellac, but since the alcohol only makes you dizzy, and isn’t stored inside your internal organs for very long; most don’t think one is required as they drink their favorite whisky while applying shellac. :-)
Be safe with solvents, always read MSDS and use proper protective equipment (PPE)! If you dissovle your own flakes in hardware store alcohol which has poisonous methanol in it, always wear PPE!

Finding retarders or solvents can be challenging thanks to US government rules written by EPA and alternate uses monitored by DEA and Homeland. Rules are simple: Solvents must be handled, and disposed of properly by educated law abiding people, hence they are only sold at dedicated purpose stores that keep records of sales.
Can generally find retarders and solvents are any auto painting supplier, industrial wood working finish supplier, or laboratory supply (most expensive). Not ever brand store (PPG, SW) carries very type of plain retarder solvent, so be warned you may have to shop around. Do not forget to read MSDS as many branded retarders have product names/numbers and will not say that it is PGMEA, MAK, or common blend of PGMEA/MAK.

Best luck on your finishing solvent adventure!
Hope this helps.

PS – I am just another useless idiot posting information in a web forum that may or may not be 100% accurate. The above is simplification and may not agree with others scientific definition of retarder solvents.
So, YMMV

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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CWWoodworking

484 posts in 568 days


#8 posted 05-19-2019 12:35 AM

IMO, shellac shouldn’t be used in a mud room. (For me, anywhere).

If your willing to spray, just use a lacquer based product. You can find better, more appropriate product.

View rustytools's profile

rustytools

7 posts in 1193 days


#9 posted 05-19-2019 12:49 AM

I don’t finish much with shellac but I use it for a seal coat under a lot of finishes. When I use Zinnsser seal coat I cut it 1 to 1 with alcohol and apply it with a pad. I do the same if I’m doing a full finish with shellac I just don’t finish anything vary big with shellac. On small areas if I get laps I let it dry and quickly wipe over it with a pad and just alcohol. You have to wipe it quickly and you don’t want the pad dripping, just moist. The pad is a lint free rag balled up and rapped by another lint free rag.

View Rich's profile (online now)

Rich

4483 posts in 978 days


#10 posted 05-19-2019 04:01 PM

I just ran across this article by Flexner. He says lacquer retarder can be used to slow the drying time for shellac. Who knew?

www.popularwoodworking.com/article/5-common-spraying-problems

I use Sherwin Williams K27 retarder thinner in my lacquer. Any of their stores can order some for you, or if you have a commercial SW store, they almost always stock it. Mohawk offers it too.

-- Knowledge is not skill. Knowledge plus ten thousand times is skill. -- Shinichi Suzuki

View bilyo's profile

bilyo

694 posts in 1492 days


#11 posted 05-19-2019 08:03 PM


I just ran across this article by Flexner. He says lacquer retarder can be used to slow the drying time for shellac. Who knew?

www.popularwoodworking.com/article/5-common-spraying-problems

I use Sherwin Williams K27 retarder thinner in my lacquer. Any of their stores can order some for you, or if you have a commercial SW store, they almost always stock it. Mohawk offers it too.

- Rich


I recently did the same. Don’t remember if it was the Flexner article or not, but I did find information on using lacquer retarder. I sprayed shellac on a complicated rocker and added some retarder. It did not have a huge effect (but only used a small amount), but did allow me to use a more relaxed pace and improved leveling. No side effects were noted.

Shellac.net offers a shellac retarder that they say is not lacquer retarder.

View CaptainKlutz's profile

CaptainKlutz

1360 posts in 1883 days


#12 posted 05-19-2019 10:53 PM


I just ran across this article by Flexner. He says lacquer retarder can be used to slow the drying time for shellac. Who knew?
www.popularwoodworking.com/article/5-common-spraying-problems

I use Sherwin Williams K27 retarder thinner in my lacquer. Any of their stores can order some for you, or if you have a commercial SW store, they almost always stock it. Mohawk offers it too.

- Rich

LOL, I knew. Am a stupid materials engineer, one that engineered many solvents, adhesives, & polymers in past before retirement. I like Flexnor’s work, refer his book myself occasionally. I just wish that Flexnor articles had the space to actually explain why things works, and not use one liners like the above article? Hardest part of his magazine work is brevity misses things that can help folks understand why/how things work well. It’s not his fault, it’s the challenge with any commercial published materials. :)

FWIW – I find that commercial retarder blends like Sherwin Williams K27 for lacquer or the multitude of others to be much more expensive than using a single slow evaporation solvent like PGMEA or MAK. Cost difference is almost half, which is not trivial when can only buy gallons of blended solvents @ $30-50 each retail.

The local ‘Painter's Supply’ sells quarts of Lowchem LR-236 (PGMEA) for $6 and gallons for $19. If you spray gallons of finish per week, then gallons of retarder solvent work well for you. But retarder is supposed to be 10% maximum of total liquid, so a quart can last me a year when I am only in shop a couple times a month.

If don’t mind using a blended retarder, many Ace Hardware and True Value hardware stores sell Sunnyside or Jasco branded retarder solvents, usually in handy quart sizes for ~$10-12.

Just remember that blended lacquer retarders ingredient lists look like this:
Sherwin Williams K27:
Methyl n-Amyl Ketone
2-Butoxyethanol
Aliphatic Hydrocarbon Solvent
Aliphatic Hydrocarbon
Methyl-1-propanol
Toluene
Xylene
Ethylbenzene

SunnySide Lacquer Retarder:
Xylenes
Ethyl Benzene
n-Butyl Acetate
n-Butyl Alcohol
2-Butoxy ethanol

Please be aware that ethyl benzene and some ketones are mutagenic carcinogens. It not only messes up your body, but can also mess with your future offspring well being. Always use PPE with solvents!

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View ohtimberwolf's profile

ohtimberwolf

931 posts in 2741 days


#13 posted 05-20-2019 02:35 AM

Wow, lots of great info coming in. I never knew it could be so complicated.

CWwoodworking: I would like to know why you feel as you do about shellac, just wondering, I might learn something. larry

-- Just a barn cat, now gone to cat heaven.

View Walker's profile

Walker

159 posts in 861 days


#14 posted 05-20-2019 02:59 AM

Apply the shellac in my basement! : ) With nearly no ventilation or air movement, high humidity, and low temperatures…seems like everything takes days if not weeks to dry!

-- ~Walker

View CWWoodworking's profile

CWWoodworking

484 posts in 568 days


#15 posted 05-20-2019 01:59 PM


CWwoodworking: I would like to know why you feel as you do about shellac, just wondering, I might learn something. larry

- ohtimberwolf

The few things that shellac is good at(sealing stains or knots, toning/shading) I don’t use.

I hate finishing so I keep it simple-stain, 2-3 coats of lacquer.

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