Large Scale Central

DIY Paint hood/booth

Tools and Tips
#13

I never had a Spray booth with a fan for exhaust in it… All my painting
was done in the garage with a plain cardboard box to keep the spray from
going everywhere… I bought a cheap lazy susan, placed a board on top of it then a
few pieces of newspaper over it all, the placed the model I wanted to paint on it
and painted it being able to turn it 360 degrees…

That was fine for the railroad cars, but the Colorado Models buildings we painted on a
piece of plywood placed on saw horses and covered with newspaper… These buildings were
painted before assembly…

When we painted in the garage, we’d raise the garage doors a few inches to get some air flow
after we were done painting, letting the paint dry…

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#14

Speaking of paint booths I have been custom painting models for some 60 years and have used a paint booth for most of that time, but I would like to add here that most of my models O and G gauge are painted out in the open. I say this not that painting with good air flow is not important for both health and dust free models, but painting in a small booth does not have the correct painting room to move and rotate the models for a proper paint job. Most of my models are paint outside with one hand holding the model and the other with air brush, or rattle can in the other, this does two things, giving good light and rotation to see how the paint is flowing on the model. I will say here that dirt in the paint is not a problem and no more then air flowing though a paint booth will get. I will also say that I live in Texas where I can pick good days to paint, warner weather and no wind, I do realize that different parts of the country may not be so lucky for good weather conditions. I would also like to say that good paint jobs are from knowledge of painting and this only comes for time and learning paint skills, not so much from a paint booth which does not make you a better painter of quality model results. Painting your models does require skills, can you look at your models that you are painting and tell what the results will be, do you have too much paint on it, or not enough, I can and this comes for all those years of experience and yes I have made every mistake in painting known to mankind.

trainman

#15

I’m with John - rattle cans should be used outdoors. I seldom paint indoors unless it is brush painting acrylics.

#16

Unfortunately I live where I’m lucky to see a high of 40F this time of year :cold_face:
I heat exclusively with wood, the only area in the house that sees 65F is where the box is placed,
about 15’ from the main fireplace.

#17

Devon me boy, those are all great pipe dreams. In order to capture paint particles (over spray) you need an air velocity of 100-150 feet per minute velocity. So lets say you build a booth that is 2 feet high x 3 feet wide, or 6 square feet. To maintain the required velocity you need a fan that will move 6 sq feet times 500 feet per minute velocity or 600 cubic feet per minute, and that will need to be at a minimum of 2" static pressure. Bathroom fans don’t even get close.

The static pressure requirement is to overcome the pressure drop across the filters that will need to be no less square footage then the entrance to the booth. Filters need to be equal to the best filters you would buy for your home for air purification. The filters need to be upstream of the fan and have a reasonable transition from the square shape of the filters to the round shape of the fan inlet (for least pressure drop.

Next the fan needs to be a squirrel cage type fan, preferably a backward curved or radial tip type tip to get the static pressure needed. The backward curved fan will be quieter than the radial tip.

This is a thumb nail description of what is needed for an efficient paint booth or hood. I would recommend doing some research online to see if there is anything available for booth/hood design information. My books are currently packed or I would sketch out a rough design for you. I promise you will not be satisfied with a ‘bathroom fan’ design in the long run. Home made can be cheaper, and sometimes better than store bough if they are done right.

#18

I can’t recall where you live Andy but one of the issues with garage painting is temp. I would miss at least 4 months of painting time. Plus as a wood worker I have way too much dust to contend with. I would love nothing more than to set up a spray booth in my garage not only for my modeling but my wood working also. But between weather and dust that just isn’t a reality.

Unless I can talk the wife into moving and building me a 50 by 100 shop with a upstairs enclosed heated hobby room. . . . :thinking:

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#19

Now that is a [Bob_Cope] great pipe dream!

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#20

The open end of my booth is 20" x 47".
The only specs I have for the fan are:

The Lasko 20 in. 3-Speed Box Fan combines the cooling power of 3 fan speeds with the wide-area air flow of 1820 CFM air circulation and a 20 in. fan

So it would appear to have 2x - 3x the necessary air flow, no idea about static pressure…

I have been keeping a close watch on the surrounding area. There is a LOT of over-spray inside the booth, the filter is covered. But there is absolutely no sign of particles either on the fan blade, the area outside the opening, or the area on the discharge side.

#21

Devon, I am in southern illinois, 50 miles east of St Louis… Have a 3 car garage, so painting was done in the 3rd stall… Garage is insulated and during the winter, when we park the vehicles inside, the heat from the engines cooling down heats up the garage a tad… :slight_smile:

#22

I did more research:

In an AC induction motor we only need to supply the power to the stator and power is induced in the rotor and hence no sparking occurs.

my source

Granted a bad connection could cause a spark…

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#23

The information I provided, as I said, is only a thumb nail of the total to construct a ‘proper’ paint booth/hood. This is from memory, been out of the air handling industry for 15 years. One of the other fora had a good thread on paint booths, but the one I think it is, I am currently locked out of, like BD they just changed software and I haven’t gotten to update my membership.

One of the BIGGEST bug-a boos in low cost paint booths is the fan motor. Most inexpensive fan motors will put the motor in the air stream, and if the user is painting with VOC paints, that can be a dangerous situation. A proper system will either have a belt driven fan keeping the motor out of the air stream, or an explosion proof motor (high dollar).

I realize this is a hobby, but no sense in promoting dangerous processes for the sake of cost. I will get logged back into the other forum and see if I can locate the thread.

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#24

Found the link I was speaking of Spray Booth - DIY Build - the MRH Forum

#25

Bob,

I for one appreciate the knowledge and is the reason I made the post. I know less than nothing about air handling. I say less than nothing because what I think I might know could be wrong and in this case outright dangerous. I was spit balling ideas. Clearly not having any clue about unforseen dangers.

The info you included here is gigantically important and has made me completely reconsider what I want to do. While I like to do DIY projects, and many steer away from them for fear of doing something dangerous, I believe armed with good knowledge and proper planning one can do a DIY project safely.

You have not deterred me, you have educated and encouraged me. Armed with this knowledge I still think I can do a great job, but do it safely.

#26

for spray painting i need the garden, a model, a spray can and a cigarette.

step one: light a cigarette, to establish the direction of wind.
step two: turn back to luv, and model to lee.
step three: put out cigarette.
step four: spray paint (preferably onto the model)
step five: search for a place, where to put model for drying.
step six: go and wash hand that held the model.

if its raining, any large cardboard box is good enough.

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#27

Wow, if I took all these facts and had to have some type of paint booth just to get my models painted I would have not ever sprayed painted models, etc. in my life. Being a retired body shop mgr. for a large DFW GM dealer I’ve seen it all where it comes to spray painting and so far the world still go on. If you over think this topic you will probably never achieve your goals to to becoming a good model painter, you can over think to to death. Many of you have good and practical approach to model painting, the others are still trying to figure how to get the spray booth to paint the model for you.

trainman

3 Likes
#28

Us over think. . . The horror

#29

I agree. Browse something like this:
hobby spray paint booth (in images)

and then go for it. Consider the safety issues we’ve discussed … but don’t get anal. On that point
I feel safe with my design as it uses an AC motor, and doesn’t compress the airflow into a contained
area (as some of the ducted designs do). I suppose a “flare off” could happen but there would be no explosion. I do keep an extinguisher handy…

Disclaimer: if you DO manage to blow yourself up, don’t blame me!
I’m just sharing info on how I did it, and NOT suggesting you do the same.

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#30

Looking at that picture I realized I did have a serious safety issue, so I fixed it:

IMG_20220120_084502835_HDR
IMG_20220120_084502835_HDR1920×1440 180 KB

#31

One thing to consider, whether you’re buying or making is: have LOTS of light. I doubt you can have too much. You probably won’t consider it until you start painting. I like Steve’s light - looks nice and bright.

#32

It could almost use two strings of LEDs, one to the rear and one to the front. With just the one you get shadows on one side or the other depending on where you hold it.