Funky Shellac

[Julie Moriarty]

For the first time, I sprayed shellac today. It was made from super blonde flakes and diluted in Behlen alcohol. I've ragged it and brushed it on but I wanted a nice finish so I sprayed it today.

The orange peel was substantial. FWIW, I've sprayed lacquer to a degree almost devoid of orange peel but by no means would I call myself highly skilled at spraying. But based on what I saw, I'll say the orange peel was the result of my inexperience.

Then came the really weird...

When I went to clean the spray gun, I took alcohol and ran it through the gun. After it ran through, I looked in the cup and saw amber colored clumps. And in the container that I was draining the alcohol into, as it ran through the gun, I saw amber clumps gathering together. When I placed the sprayer components in the alcohol, they attracted the amber clumps. I began thinking, Invasion Of The Shellac Sprayers!

I ended up cleaning everything with lacquer thinner and that did the job.

I've sprayed WB finishes with this gun. I've sprayed lacquer too. All with no problems. So why would shellac create this?

[Rich Engelhardt]

So why would shellac create this?

Probably water.
I'd suspect the alcohol.
Alcohol is hydroscopic - it will wick water out of the air if the cap isn't tight and/or if the can is left open.

You can test this by mixing up a small amount of the flakes and some rubbing alcohol. Rubbing alcohol is usually about 60% or so water.
Shellac thinner aka denatured alcohol is usually about 97% or better pure.
Shellac will "Clump" like you describe when the water content is around 10% or so - so it doesn't take a lot to make the shellac unusable for thinning.


Another possibility is that the WB left some residue.
Nearly all WB coatings use some form of ammonia as a solvent in their formulation.
Ammonia is the natural solvent for shellac also.

Tip - use cheap ammonia to flush your spray equipment, then rinse with expensive alcohol.

Yet a third possibility is some sort of metal contaminate, such as a zinc or zinc soap in the spray equipment.
I was reminded just last week how much shellac hates solder joints.....
Somehow the lining of a gallon of Seal Coat I had got scratched on the solder joint. It ate through and leaked all over the place.
Thankfully, it just ate through. The last one I had built up enough pressure to blow the lid.......talk about a mess....

[Jason Roehl]

Nearly all WB coatings use some form of ammonia as a solvent in their formulation.

You're going to have to cite some MSDS sheets on that one.

http://www.paintdocs.com/webmsds/web...pe=MSDS&lang=E

http://www.ugl.com/pdf/ZAR%20Wood%20...20-%20MSDS.pdf

https://buyat.ppg.com/ehsdocumentman...hControls=True

Those are just a few random MSDS sheets from a Google search. I've taken many a whiff of paints that smelled like ammonia, but there's no ammonia on the ingredients list or the MSDS (and ammonia is common/dangerous enough to warrant inclusion). Instead, you'll find that paints are often acidic, containing something like propenoic acid--which would react with any ammonia were it an ingredient. In fact, I suspect that paints are generally acidic because that allows for a chemical etch to promote bonding.

On edit: Propenoic acid is also known as "acrylic acid". Sift past the chemical jargon, and you'll see why it's in WB (acrylic) coatings:

http://en.wikipedia.org/wiki/Propenoic_acid

I'd be more inclined to go with your other contaminant theories. I've sprayed LOTS of shellac, and I've always done a first rinse with off-the-shelf denatured alcohol, even old, open, rusty, half-full cans, and never had chunks result. Successive rinses are then done with a strong ammonia solution.

[Jason Roehl]

As for Julie's problem, I suspect there is a basic solution, regardless of what the actual cause of the problem was:

Good spraying practice is, even when your spray gun is absolutely clean from the previous spray session and (immediate!) cleaning, to run the pure solvent of the material you're spraying through the gun before you begin. In the case of shellac, this means to run some denatured alcohol through the gun before you put shellac in it. That way, if there are any dried finishes or pools of other solvents (including water) that are sensitive to the material/solvent you're spraying, you'll know about it before you put your material in the gun.

This is especially important when switching back and forth between coatings that have different main solvents.

[Prashun Patel]

How new are your flakes? While it's common perception that flakes will keep indefinitely, old flakes that have been subjected to varying temperatures and humidity can fail to dissolve in alcohol; they get clumpy and gooey as you describe. However, you would have seen that in the solution. Did you mix the shellac in the spray cup directly or did you mix it in a different vessel?

Also, what cut are you spraying? I get the best results with thin cuts like 1-1.5#

[Rich Engelhardt]

You're going to have to cite some MSDS sheets on that one.

You have to keep in mind - - the MSDS isn't a comprehensive list of all ingredients.
If ammonia is used in the production of an acrylic resin for example, it doesn't have to be listed on the MSDS - even though the ammonia itself may be hazardous.

[Jason Roehl]

You have to keep in mind - - the MSDS isn't a comprehensive list of all ingredients.
If ammonia is used in the production of an acrylic resin for example, it doesn't have to be listed on the MSDS - even though the ammonia itself may be hazardous.

Just because ammonia may be used in the production doesn't mean it's in the can of finish. It's true that every ingredient that is used as a production input doesn't have to be on the MSDS, but if it's in the can as a distinct chemical, then it does have to be on the MSDS (they list water on the MSDS sheets). All I'm saying is that if finishes are typically acidic (have acids listed on the can), then there won't be ammonia in the can causing problems as a residue when someone runs some shellac through a spray gun after it.

[Prashun Patel]

but if it's in the can as a distinct chemical, then it does have to be on the MSDS (they list water on the MSDS sheets).

(Respectfully), that's not true. We manufacture chemical blends and have to prepare MSDS's for our products. Only 'hazardous' chemicals are required to be disclosed in the composition section. (The ANSI and OSHA regulations governing what is classified as hazardous are complicated, and subject to interpretation). A manufacturer is free to disclose other ingredients like water if they wish. In fact, water may be required to be disclosed for some hazard concern itself (e.g., potential for bacterial growth).

MSDS's will change dramatically through 2015; the US is coming in line with the 'Globally Harmonized System' of chemical documentation. The hazard standards will be further reaching, so you can expect more disclosure.

I can tell you that MSDS prep and chemical disclosure is a reluctant game manufacturers of ANY proprietary blend play. In an effort to protect their intellectual property, they disclose only what they HAVE to.

[Julie Moriarty]

The flakes were bought only a few weeks ago. That's about the time I mixed them. I used Behlen alcohol to dilute the flakes. I clean with cheap stuff but mix with better quality stuff. What I haven't done was flush with the solvent for the finish I'll be using. The last time I used WB finish was about 6-8 months ago. The gun didn't get any use until I began spraying the lacquer. But there was only a week or so between the lacquer and shellac. FWIW, I always clean after spraying but only when I'm done for the day. I've also learned a lot about the gun since starting to spray lacquer. And I break it down completely at the end of the day and clean it thoroughly. I'll have to pay more attention the next time I spray shellac. I sprayed lacquer yesterday and the only problem was the seal on the cap. I cured that by replacing the gasket, which was only a month old.