I build period furniture and only use only alcohol based shellac as a finish and quite often spray it due to the fact that I am building big case pieces or pieces with complicated surfaces. I have always done so outside but this is limiting as I need to finish in the winter and at night also. I have a dedicated room off of my basement shop that has a window to the outside. I want to set it up as a spray room but want to do so safely so there is no explosion hazard. It shellac as explosive as lacquer? I know I will need an explosion proof fan. Can I safely use a regular fan with a TEFC motor? I was going to put an opening in the door to this room and leave a window open on the other side for intake air. I would put the light switch on the outside of this room but what about the light fixtures. My idea was to cover them with an enclosure made of Plexiglas. There is no other electricity in this room at all now. Any other hints or precautions. Is this a bad idea? I Don't want to put the house or family at risk. Does anyone else spray shellac in a home shop and how do they go about making it safe? Any ideas would be appreciated.
spraying shellac safely
- Thread starter Scott
- Start date
Mark Bortner
Well-known member
"Is this a bad idea?".........YES!!!
I know being able to spray is a problem many home shops have to deal with but I would rather burst your bubble than hear a horror story about something going wrong! The better the alcohol (higher proof) the closer it gets to lacquer thinner's ability to go BOOM! When you vaporize any flammable liquid that's when it really gets dangerous, think of the injectors in your car and that's very similar to what a spray gun does. A tefc motor MUST be sealed outside the air stream! If you look closely at a pic of most booth fans online you'll notice the belts and pulley are inside a tube. This is what makes them explosion proof but not if the motor is inside the booth with the vapors! You could even use an open (odp) motor with these since it would be isolated. The option is an explosion proof motor with a fan blade on it. Anything less than leaving your garage door wide open for makeup air could create enough negative pressure to suck out a pilot light if you have a gas fired furnace, water heater or dryer. Don't laugh, it happened to the water heater where I work last winter! Be careful blocking airflow to incandescant lights, they can and do overheat which melts the insulation on the wires and they short out. That's why you have to keep insulation away from can lights. Perhaps the biggest reason of all, if you ever have a house fire even if your spraying has nothing to do with it, having a booth in your basement will be all the excuse your insurance company will need to deny your claim! If you really need to be able to spray in a residential situation get one of those little 8x10 sheds dropped off in your yard, insulate it well, warm it up ahead of time and finish in that. You could get lucky for years and many people do but is it worth the gamble?
I know being able to spray is a problem many home shops have to deal with but I would rather burst your bubble than hear a horror story about something going wrong! The better the alcohol (higher proof) the closer it gets to lacquer thinner's ability to go BOOM! When you vaporize any flammable liquid that's when it really gets dangerous, think of the injectors in your car and that's very similar to what a spray gun does. A tefc motor MUST be sealed outside the air stream! If you look closely at a pic of most booth fans online you'll notice the belts and pulley are inside a tube. This is what makes them explosion proof but not if the motor is inside the booth with the vapors! You could even use an open (odp) motor with these since it would be isolated. The option is an explosion proof motor with a fan blade on it. Anything less than leaving your garage door wide open for makeup air could create enough negative pressure to suck out a pilot light if you have a gas fired furnace, water heater or dryer. Don't laugh, it happened to the water heater where I work last winter! Be careful blocking airflow to incandescant lights, they can and do overheat which melts the insulation on the wires and they short out. That's why you have to keep insulation away from can lights. Perhaps the biggest reason of all, if you ever have a house fire even if your spraying has nothing to do with it, having a booth in your basement will be all the excuse your insurance company will need to deny your claim! If you really need to be able to spray in a residential situation get one of those little 8x10 sheds dropped off in your yard, insulate it well, warm it up ahead of time and finish in that. You could get lucky for years and many people do but is it worth the gamble?
Mark Bortner
Well-known member
One other thing, the (very simplified version of the) rule for sizing a booth fan is all the air in the booth has to move at least 100 feet per minute so if the wall with the fan is 7 feet high and 8 feet wide you'll need at least a 5600 cfm fan!
Mark, Thanks for your reply. OK I guess it was a bad idea. The fixtures I was going to enclose were Fluorescent and I did figure I would probably need an explosion proof belt drive fan. The room is 12 x 14 with 8 foot high ceilings and I did not realize I would need so many CFMs of air . I could leave the garage doors wide open for make up air. That is a great point about the insurance. I will forgo this idea. I guess my only other option for spraying inside would be to use only Water based lacquer or shellac. If I did this I would not make a booth but just spray in the heated garage with smaller fans temporarily mounted in the door to exhaust the overspray. So how appropriate are these finishes for period reproductions. I guess my question would be more specifically would be: How similar would they look to alcohol based shellac? I have had great success with alcohol based shellac and it makes a beautiful natural looking finish. Would water based give me the same look? I do get much better and quicker finishes when I spray. Especially if it is something like a formal chair where brushing is more prone to runs and dripping.
dkeller_nc
Well-known member
Scott - Generally speaking, you may be a bit over-cautious in estimating the hazards of spraying a solvent-based finish. It is true that it is theoretically possible to generate an explosion from vaporized solvents and an ignition source, but it is unlikely in a home situation.
For an explosion to occur, you must have a concentration of the solvent in the air next to the ignition source that is above the LEL (Lower explosion Limit) and below the UEL (Upper Explosion Limit). Generally speaking, getting the solvent concentration above the LEL is difficult except in an enclosed, non-ventilated space. That doesn't mean it's impossible, but with a dynamic airflow in a dedicated finishing room, it's unlikely.
For an explosion to occur, you must have a concentration of the solvent in the air next to the ignition source that is above the LEL (Lower explosion Limit) and below the UEL (Upper Explosion Limit). Generally speaking, getting the solvent concentration above the LEL is difficult except in an enclosed, non-ventilated space. That doesn't mean it's impossible, but with a dynamic airflow in a dedicated finishing room, it's unlikely.
The LEL of ethyl alcohol (that’s what’s in denatured alcohol and most shellac) is 3.3 % by volume. Shellac resin itself is not explosive or flammable separate from the solvent, so its presence makes explosion less likely. I dont think it would be likely to reach that level with the 7500CFM explosion proof motor I had in mind but I will consider all the good points Mark made in his response. Insurance is a very good point. thank you.
Does the type of spray equipment factor in? I assume an HVLP systems produces much less overspray, so less volatiles would be airborne and somewhat safer. I'm not all that familiar with new equipment capabilities so I could be wrong.
I think its reasonable to brush on some early coats to build thinkness, and follow up with spray if needed. Are there any risks , hazardous or finish quality, with that approach?
Curious, and appreciate the dialog.
John
I think its reasonable to brush on some early coats to build thinkness, and follow up with spray if needed. Are there any risks , hazardous or finish quality, with that approach?
Curious, and appreciate the dialog.
John
Mark Bortner
Well-known member
As of yet I have never seen a water based clear that I'd put on any decent piece of furniture. I truly think we're at least a decade away from them looking good enough even though the EPA guys don't want to hear that! Don't get me wrong, they're looking better all the time and are fine for average craft projects. One of the biggest reasons to avoid water based is thinking ahead to future generations who will restore your pieces down the road, you're not into making throw away IKEA crap if you're on this forum! There is no way to reamalgamate a water base clear and they're not very easy to strip. HVLP will make less overspray which saves material and lessens the risk but doesn't eliminate it. Turbine units have the added bonus of warming up the air which helps flow-out but they're basically just hopped up shop vacs with universal brush type motors which make that annoying whine. Some of them spark just like a drill or router which never made sense to me at all since people sit them on the floor right by where they spray!!
Thanks Mark, I am making very high end pieces with lots of carving, veneering etc with hundreds of hours in each piece. Thats what I thought about water base. I never really thought I would put it on my pieces but just wanted to ask. Thanks for sharing all of you knowledge. Sure appreciate it. Looks like the only absolutely safe way for me to do it is to go back to the brush, Wait for favorable weather outside and spray outside or rent or borrow professional booth time. Between the three I can work it out. Once again thanks for sharing your wealth of knowledge.
Antiquity
Well-known member
Mark,
I found a water base finish that is crystal clear when dry. I've been using it for several years and cannot tell the difference between it and an oil base finish. It can be wiped on, brushed on using a badger brush or sprayed (I do not spray the but can says it can be). It is made by General Finishes. FW did an article on it and other finishes and gave it a high mark. My customers love it. I would never go back to an oil finish.
Dennis Bork
Antiquity Period Designs, Ltd.
I found a water base finish that is crystal clear when dry. I've been using it for several years and cannot tell the difference between it and an oil base finish. It can be wiped on, brushed on using a badger brush or sprayed (I do not spray the but can says it can be). It is made by General Finishes. FW did an article on it and other finishes and gave it a high mark. My customers love it. I would never go back to an oil finish.
Dennis Bork
Antiquity Period Designs, Ltd.
jim vojcek
Well-known member
Dennis
What is the name of the General Finish product? It almost sounds too good to be true!
Jim Vojcek
What is the name of the General Finish product? It almost sounds too good to be true!
Jim Vojcek
Antiquity
Well-known member
General Finishes is the name of the company. The water base finish is called "Polyacrylic". It also comes in a high performance (for table tops) called "High Performance". Four sheens are available. I buy it from my local ACE Hardware, Rockler or Woodcraft stores.
www.generalfinishes.com
Dennis Bork
Antiquity Period Designs, Ltd.
www.generalfinishes.com
Dennis Bork
Antiquity Period Designs, Ltd.
Dennis,
The ongoing thread about shellac and boiled linseed oil highlights the problem that I have had with water based finishes, i.e. the lack of depth or luster that water based finishes seem to be plaqued with. I know you have vast experience but are you telling us that side by side, on the same board, General's water based finish will have the same depth and luster as shellac or oil based poly?
Howard Steier
The ongoing thread about shellac and boiled linseed oil highlights the problem that I have had with water based finishes, i.e. the lack of depth or luster that water based finishes seem to be plaqued with. I know you have vast experience but are you telling us that side by side, on the same board, General's water based finish will have the same depth and luster as shellac or oil based poly?
Howard Steier
Antiquity
Well-known member
Howard,
In my opinion this water base finish from GF does have the same depth and luster. The more coats you apply the greater the luster and depth. Also, what's great about it, you can apply three coats in one day. I first apply a coat of shellac to seal the wood and it also pops the curl (in curly woods) and gives an old patina to the surface. If you apply the water base top coat directly over a water base stain it will interact with the stain and bleed, therefore you must apply a coat of sealer/shellac. After applying 2 to 3 coats of this water base I find that you do not have to sand in between coats. The surface is almost completely smooth and free of dust particles. This saves time with not having to always sand.
Note: it is best to use a Badger brush when apply this finish from GF. I tried regular water base brushes but they will leave bubbles on the surface.
As always you must experiment on a sample piece of wood. Brushing on water base is like brushing on milk. There will be lots of bubbles but they will dissipate within a minute or two.
Dennis Bork
Antiquity Period Designs, Ltd.
In my opinion this water base finish from GF does have the same depth and luster. The more coats you apply the greater the luster and depth. Also, what's great about it, you can apply three coats in one day. I first apply a coat of shellac to seal the wood and it also pops the curl (in curly woods) and gives an old patina to the surface. If you apply the water base top coat directly over a water base stain it will interact with the stain and bleed, therefore you must apply a coat of sealer/shellac. After applying 2 to 3 coats of this water base I find that you do not have to sand in between coats. The surface is almost completely smooth and free of dust particles. This saves time with not having to always sand.
Note: it is best to use a Badger brush when apply this finish from GF. I tried regular water base brushes but they will leave bubbles on the surface.
As always you must experiment on a sample piece of wood. Brushing on water base is like brushing on milk. There will be lots of bubbles but they will dissipate within a minute or two.
Dennis Bork
Antiquity Period Designs, Ltd.