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Forum topic by Domer posted 05-16-2011 08:52 PM 7911 views 1 time favorited 15 replies Add to Favorites Watch
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Domer

252 posts in 2833 days


05-16-2011 08:52 PM

I just purchased a Earlex HVLP spray system. i want to use it to spray furniture that I make.

It is my understanding that in order to get the best pop of the grain of the wood, that it is best to spray shellac first and then a water based poly.

I have read that you can spray the shellac outside with out any fear of fire but if you want to spray inside your garage, you need to construct some sort of spray booth. The problem I have read about is that you really need to buy an explosion proof fan and they are pretty expensive.

One guy told me that he uses a regular box fan but puts in behind him to blow the fumes out.

Any thoughts?

Domer


15 replies so far

View Steven H's profile

Steven H

1117 posts in 2527 days


#1 posted 05-16-2011 09:34 PM

Boiled Linseed oil or tung oil will pop the look of the grain.

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DrDirt

4169 posts in 3209 days


#2 posted 05-16-2011 11:17 PM

Need oil or dye to make the grain/figure pop. Then shellac will seal it.

As far as explosion proof needs – - I really don’t know. I also wonder if the need is much like the debate on grounding your dust collector. I don’t know if someone using a small HVLP system would every build up enough vapor to combust. When I spray lacquer – I shut down all the fans and then spray. Leave the shop for 15 minutes then come back and open the garage door to get rid of the fumes (which the fan won’t do for you either unless you vent it to the outside)

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

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Alan S

178 posts in 2784 days


#3 posted 05-16-2011 11:57 PM

I wouldn’t mess with spraying things like lacquer inside without proper ventilation (real spray booth). I have been researching this lately too and it seems that the risk of EXPLOSION is VERY REAL! Much more real than dust collection and static.

Alan

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Jack_T

623 posts in 2498 days


#4 posted 05-17-2011 05:52 AM

Shellac and lacquer are both highly explosive. If you are going to spray indoors you have to have a proper spray booth. Check the MSDS sheets for both.

On the other hand you have nothing to lose other than your life, your house, the contents of your house and your family if the happen to be in the house when it goes up in flames. No real reason to be cautious. Of course I am being sarcastic to make a point.

-- Jack T, John 3:16 "For God so loved the world that he gave his only Son, so that everyone who believes in him might not perish but might have eternal life."

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Loren

8314 posts in 3115 days


#5 posted 05-17-2011 08:27 AM

If you spray shellac you have to clean the gun with denatured
alcohol.

I don’t see a real strong reason to spray shellac as an undercoat.
It “pads” on beautifully and fast. That’s one reason it’s a favorite
of many pro furniture builders.

You can still topcoat with waterborne through the gun. It is
a bit easier to clean up after.

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Les

201 posts in 2158 days


#6 posted 05-17-2011 01:51 PM

If you use water based shellac you won’t have to worry about the fire hazard.

Les

-- Stay busy....Stay young

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DrDirt

4169 posts in 3209 days


#7 posted 05-17-2011 11:22 PM

Okay – have to ask – two posters have gone down the “oh my god we’re going to die road”

If you are going to spray indoors you have to have a proper spray booth”
“I wouldn’t mess with spraying things like lacquer inside without proper ventilation (real spray booth).”

Is this what you THINK or what you KNOW.
a “Spray can” and a spray gun are the same thing. Did you set up a booth when you got out the can of Deft spray lacquer?
How about that Highly explosive can of Krylon you let the kids use in the garage??
Obviously you would want a professional setup if you had a lot of spraying – and waterbased gets around a lot of the issues.
My comments are really about SCALE of the operation. If I am going to spray kitchen cabinets in a 10X 10 area… that is one thing. If I am going to spray a jewelry box in a 2 car garage….. that is another.

EDIT*
Did some research and the LEL (Lower Explosive Limit) for Lacquer Thinner is 1% (by Volume). Pretty low – Methanol is more like 5%.
My shop is a 1 car garage – 14X21 with 12 foot ceiling. That works out to 3528 cubic feet. 1% of that is 35 cubic feet.
35 cubic feet is roughly 990 liters
Using old freshman Chemistry 1 mole of gas is 22.4 liters so 990 liters/22.4 liters/mole is 44 moles.
The Molecular weight of Acetone (primary ingredient) is 58 grams/mole. So we have 2580 GRAMS of Acetone.
The DENSITY of Acetone is 0.79 grams/ml (water is 1.0) so I would have to have 3265 ml (or ~3/4 of a gallon ) of solvent (not including the solids from the lacquer) suspended in the air to reach the minimum concentration needed to ignite.
My Lacquer is ~25% solids so I would need to seal my work area and spray the entire gallon of lacquer to get to that 1% level. For me that just isn’t ever going to happen. I don’t plan to ever try to come close – I usually only ever spray <1liter at a time and the work area is far from sealed.

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

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Alan S

178 posts in 2784 days


#8 posted 05-18-2011 02:40 PM

DrDirt: To me the margin your calculations show are nowhere NEAR high enough for me to risk my life and my families lives. Basically, you are talking about a 3:1 margin of the safe limit vs what you will do in your shop. Any variables unaccounted for can EASILY eat up that margin.

The one thing that glares out at me is that the solvent is not going to just be uniformly distributed within the volume of your shop. Upon spraying, it is going to have a much higher concentration right around where you are spraying. The density of acetone you gave is much more dense than air, so after a while, it is going to become concentrated at your feet. To me, these highly concentrated areas could EASILY pass the minimum concentration needed to ignite when spraying the amount of finish you are talking (< 1 liter).

Do what you want, but for me, your calculations show that a typical finishing scenario leads to conditions that are WAY too dangerous without an appropriate setup.

Alan

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Gregn

1642 posts in 2451 days


#9 posted 05-18-2011 05:39 PM

In my opinion the reason for explosion proof fan motors in spray booths is because of the high concentration of fumes that build up in a spray booth. In the past I have sprayed in the shop using a non explosion proof fan to draw out fumes to the outside. The amount of fume concentration for small projects has been generally no more than using a spray can of finish with a fan to help out drawing the fumes to the outside. I have done several small projects at one time and found that I had no problems due to the constant repositioning of the projects being sprayed. When I have done large projects I generally set up a temporary spray booth outside using portable frames of 2×2s covered with plastic that has no ceiling. Right or wrong this my opinion and what I have done.

-- I don't make mistakes, I have great learning lessons, Greg

View DrDirt's profile

DrDirt

4169 posts in 3209 days


#10 posted 05-18-2011 05:45 PM

Ditto grogs experience.

But there are those who feel that if you don’t have a classy booth and a full hazmat suit to use a can of Krylon” everybody is going to die”

There is a happy medium out there. A lot of these concerns are much lower with the new waterbased and low VOC finishes but every home project doesn’t require a waiver from the EPA with firetrucks and the streets blocked off.

Cheers

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

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TJU

72 posts in 2124 days


#11 posted 05-18-2011 05:59 PM

Drdirt, The chemistry teacher in me is impressed.
I think that I agree with what you are saying. Spraying small projects with lacquer or shellac in no big deal with a good mask and a fan in the door or window. I do it all the time. Here is a current post that seems similar to what you guys are talking about.
http://lumberjocks.com/topics/26977

Tim

-- Although the voices aren't real they have some pretty good ideas.

View Alan S's profile

Alan S

178 posts in 2784 days


#12 posted 05-18-2011 06:39 PM

I get what you guys are saying. The risk of explosion from spraying small projects is pretty low. I am just starting out with spray finishing as well. What I got out of the post Tim linked to is that there are alternative finishes that aren’t flammable and supposedly look similar to lacquer. Since my shop is a two-car garage integral with my house and my wife in the next room, I try to err on the side of caution when it comes to these kinds of things. I will be trying some Target Coatings water based products in the near future and hopefully get good results, so I will only have my lungs to worry about.

Alan

View Domer's profile

Domer

252 posts in 2833 days


#13 posted 05-18-2011 11:14 PM

All,

Thanks for all of the responses. Although there are several different theories about the dangers of an explosion with a home made spray booth, I have learned a lot for all of you.

There is a guy at our local Woodcraft Store who has done a lot of spraying in his garage. He tells me that using shellac, he puts a box fan behind him pushing the fumes out the garage door. He puts a furnace filter in front of the fan and another filter in the spray booth exhaust section.

I called General Finishes to see how their water based products compared to shellac. They told me their Endrovar product produced a finish very similar to Armor Seal which is what I have been using. I asked they guy from Woodcraft and he said they did not get the same finish as it lacked the pop with walnut.

Even so, it think I will try a quart of the Endrovar to see how it works as I do want to stay with the water based products.

Again, thanks for all of the input.

Domer

View SteveMI's profile

SteveMI

954 posts in 2761 days


#14 posted 05-26-2011 04:02 AM

I have and use an Earlex HVLP. The amount of air the turbine puts out makes the finish near dry after spraying and the overspray is almost non existent. Most all of my experience has been with water base but I would think the same premise holds.

When I sprayed the same water base previously with a air compressor or air brush type gun the finish was wet for some time after the spraying.

As drdirt pointed out, the air needs to be holding enough flammable vapor suspended to make that a risk. At that point you would have breathing issues.

Steve.

View steve's profile

steve

363 posts in 1460 days


#15 posted 02-24-2013 12:16 AM

OMG, people have many opinions and tend to OVER-complicate.
There are no more scientists here than on Gilligans Island…
Spray away!

-- steve/USA

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