# Air to Material Ratio



## Jason (Feb 27, 2011)

For an ultrafine splatter (fine sand finish mimic), how much airflow in CFM would you want per gallon/minute (.13368 CFM)?

I'm guessing it might be as high as 200:1 @ 100psi to produce a fine sand stucco look from a thick material? About 23 CFM to atomize 1/5 of our buckets per minute?


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## Philma Crevices (Jan 28, 2012)

Since noone else has taken a stab at this... 

First what type of rig are you thinking of spraying with, 2nd how many sq ft of wall. Also there are different types of sand finish, are you spraying to match an existing or new construction?


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## Jason (Feb 27, 2011)

Philma Crevices said:


> Since noone else has taken a stab at this...
> 
> First what type of rig are you thinking of spraying with, 2nd how many sq ft of wall. Also there are different types of sand finish, are you spraying to match an existing or new construction?


 
Thanks Philma. I looked into both progressive cavity and peristaltic pumps for spraying aggregated acrylic (with fine sand) but they both have problems I don't want to face so I've been investigating pressure tanks. Seems like a reasonable system for low-build aggregated acrylic application. The Graco RTX1500 hose pump only pushes at 100 psi, so I'm hoping a 100 psi pressure tank with a 1" or 3/4" line will perform as well. 

With non-aggregated materials, such as drywall mud or smooth acrylic, I could use a Titan airless. I got excellent results test spraying drywall mud with it (supported by a builder's yard screw compressor) but I'm resistant to putting sand through it. The 12000sv isn't sold in Australia except by individual order from the US, nor are lots of it's parts, so I try to treat it with kid gloves. And it's still pretty new and clean so I'm still enjoying the honeymoon phase.  I found I could mimic an aggregated sand finish effectively using a smooth mud but the sand-mix acrylics are about 1/2 the price of pure acrylic, so it seems wise to get myself something I can put sand through and keep the Titan for smooth stuff like drywall and elastomeric skins.

I honestly can't say as to the size of the job. I'll probably find myself quoting anything from a little old lady's front porch (howzabout a nice hip saver deck coating too, grandma?) to industrial scale tilt-up cast concrete, but I haven't worked for a homeowner for over a decade. I tend toward the larger runs afforded by new construction, even though it means dealing with these jackass builders.

Probably won't be doing much matching in with existing texture. That's a skill I have to take my hat off to. I'm planning on providing builders with a samples book for both outside acrylics and indoor drywall textures and letting them pick one from the menu.

I figure that in calculating my air requirements, I should account for the absolute finest atomizaton I'll need for a reasonable rate of material application. I've investigated gas powered screw compressors since 240v 10 amp power here won't drive much and I can't expect access to 3 phase everywhere I go. I liked the look of the Kaeser M17, which will push 60 CFM and will fit in the van. (Will be getting a trailer at some point so don't want to get a tow behind compressor.) CompAir has a similar model.

But OMG the prices on these things. The Kaeser is about $12k and that's one of their smallest. I've been told that even 100% duty cycle reciprocating compressors aren't really 100% duty, and I'll kill one if I run it continuously. The biggest gas powered recip compressors (about $5k) seem to push about 25 CFM so I figure it would be running almost all the time if I'm spraying a finely atomized finish and expecting decent progress. Also, the tanks are ungodly big and heavy on recips and don't do much for me as a texture sprayer, so I'm leaning toward the screw compressors. 

But is 60 CFM overkill? I reason it would have me set up for expansion into peristaltic pumping systems if I ever got into higher build renders or spraycrete, and it would let me blast through wall and floor acrylics quickly, but it's an awful lot of air by most texture spraying standards. Not sure if I'd be wasting money and never touching the second 30 CFM. Also not sure if there are drawbacks to screw compressors that I'm unaware of since I haven't worked with them much.


Sorry for the War 'n Peace imitation. :blink: Didn't want to leave anything out.


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## Philma Crevices (Jan 28, 2012)

Way above my payscale 
I know a good person to ask though, Rick!! you around buddy? 
PM http://www.drywalltalk.com/members/rhardman-813 I'm sure he would have some good input


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## Jason (Feb 27, 2011)

Philma Crevices said:


> Way above my payscale
> I know a good person to ask though, Rick!! you around buddy?
> PM http://www.drywalltalk.com/members/rhardman-813 I'm sure he would have some good input


 
I don't like my chances with Rick, lol. :whistling2: 

It's cool. I'll find out the cfm of the builder's compressor and check my material volume. I'm in no rush to drop that kind of money anyway. Ought to find out how far I can push my hardware store compressor first.


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## rhardman (Jul 7, 2009)

Jason said:


> I don't like my chances with Rick, lol. :whistling2:
> 
> It's cool. I'll find out the cfm of the builder's compressor and check my material volume. I'm in no rush to drop that kind of money anyway. Ought to find out how far I can push my hardware store compressor first.


Well that wasn't very nice. 

Interesting dilemma...but easy to remedy. For $2500.00 my dad built a rig that had no moving parts in contact with the mud,* would spray a primer fog coat over interior walls and heavy knockdown stucco exterior. Virtually any thick material able to pour and any thin aggregate/fluid formula that would suspend the sand (or whatever) finish.

It lasted for years without a single problem. 
But you didn't want my opinion so excuse me for butting in.:whistling2: **

Rick

(* I did confirm what you already know about the rig you need...and the other answers are...pressure regulator....more than 30...ball valve....pulsation chamber....large diameter broad wheels and 20. :jester


Still don't get it? Go to post 17 here and see a small version I made for touch up and matching textures.
http://www.drywalltalk.com/f8/what-texture-sprayer-you-sugest-1822/


_(** ...just playin' my friend!:thumbsup_


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## Jason (Feb 27, 2011)

rhardman said:


> Well that wasn't very nice.
> 
> Interesting dilemma...but easy to remedy. For $2500.00 my dad built a rig that had no moving parts in contact with the mud,* would spray a primer fog coat over interior walls and heavy knockdown stucco exterior. Virtually any thick material able to pour and any thin aggregate/fluid formula that would suspend the sand (or whatever) finish.
> 
> ...


Just 'cause I gave you such a hard time in the past, Rick. :jester: I appreciate the input tho man.

Picked up a cheap pressure vessel to experiment with so next time I come 'round I'll be typing with 8 fingers.


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## rhardman (Jul 7, 2009)

Jason said:


> Just 'cause I gave you such a hard time in the past, Rick. :jester: I appreciate the input tho man.
> 
> Picked up a cheap pressure vessel to experiment with so next time I come 'round I'll be typing with 8 fingers.


 
_*Ahhhh we're just havin' fun!!!* :thumbsup:_


My dad built an upright steel tank on wheels about 18 inches in diameter and maybe 40 inches tall. You need to make sure you have an authentic pressure cap on it. The bottom of our tank was flat but I think rounded would be better. Put a 2 inch pipe out the bottom of the tank with an elbow and then reduce it to what you need for your material hose. We used 1 inch and 3/4 if I remember right.

I would guess it to be around 30 gallons. He mounted a 12 hp electric start gas engine on a small trailer powering a 20 cfm compressor. Since the air from the compressor pulsates, you need to take a 4 inch piece of pipe, at least 30 inches long, with bell couplers on each end to make a pulsation chamber which smoothes the air flow out. In the bell caps have 1/2 inch pipe thread and then reduce them down to 1/4 inch to connect your hoses to. 

Mount a regulator on the top of the lid. The air comes from the pulsation chamber and you can dial in whatever pressure into the pot to drive the mud. Out the other port of the regulator you run your air hose to your spray gun. The mud pressure varies with what you're doing (obviously) but with a gauge on it, you start getting an idea of what you need real quick.

Steel was way too heavy and our wheels were too small diameter and too thin. It made going up porches and across grass a two man operation.

I think we used around 75 feet of hose. Be sure to use a follower plate over the mud or when it empties you'll get a "squirt" of mud that will ruin the entire ceiling.

We used the traditional pole gun with a ball valve for everything from fog coat to stucco. Worked great.

:thumbup:

I think the way to start would be to find an old compressor tank of the right size, cut off one cap, get it sand blasted and then go find a good welder...it would be the least expensive way to go. My dad had his built from scratch an overkill thickness which was why it was so heavy.

Oh...make sure to have drain plug mounted on the bottom of the pulsation chamber and a port welded in the lid for a pressure relief valve. We didn't have a handle on the lid...that might have been better.


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## Jason (Feb 27, 2011)

rhardman said:


> _*Ahhhh we're just havin' fun!!!* :thumbsup:_
> 
> 
> My dad built an upright steel tank on wheels about 18 inches in diameter and maybe 40 inches tall. You need to make sure you have an authentic pressure cap on it. The bottom of our tank was flat but I think rounded would be better. Put a 2 inch pipe out the bottom of the tank with an elbow and then reduce it to what you need for your material hose. We used 1 inch and 3/4 if I remember right.
> ...


Thanks for taking the time to type that all out, Rick. Very cool of you. I have similar ideas, but not so ambitious with the volume of the tank, although that would be pretty nice to just spray 'n forget about refilling. Figure I'll strap it to a dolly and keep the material line around 30' of 1" if I can push through that (but with a 2" elbow on the outlet). It'll mean more feeding the tank but I've got space limitations unless I set up with a new vehicle and massive trailer, which isn't happening until I see some profit from this hairbrained venture.

Also don't have your dad's skills when it comes to engines and compressors so I'm going to have to shell out for that. It'll be a honda recip, maybe 35 cfm if I can carry it, along with a hose reel that will accomodate 3/4" or at least 1/2" air hose. It'll be a noisy monster so I'm hoping to leave it stationary and just move the material tank, but if I can get them to put a mini-tank on for me it might come along, which would mean a lot less space and money on gigantic air hose. Screw compressors are just way too big and expensive for me at this early stage of the game so that'll have to stay as part of the Dream Rig.

I priced the Graco and Binks pressure tanks and got my feelings hurt pretty bad. The weight, 3/4" or 1" elbows and no follower plate! Wtf. And then they told me the price.  You mean... each?


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## Jason (Feb 27, 2011)

Whoops. Double post. Got me all excited. Hoping to do some work on her this weekend.


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