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Cross Draft Issues

#1
Just looking for opinions on what I can do to help reduce the trash I am getting in my collision jobs. I switched to SPI clears last year and I have been able to match OEM finishes consistently, but I am getting lots of trash in my jobs. By the time I sand out the trash, the repaired panels look so much better than OEM. I have a cross draft booth and have tried evyerthing I can think of to reduce trash. I have a new air hose, 3 stage desiccant with new beads, and new booth filters. I have tried leaving the fan on the entire time I am spraying from start to finish. I have tried cutting off the fan between coats. Wetting the floors and not wetting the floors. I am taping my paper and plastic sheeting to the concrete floor so that trash is not coming from underneath the cars. Nothing seems to help. My dad purchased this booth close to 15 years ago and I have only seen a handful of jobs come out of the booth that were clean enough that they did not need buffed. I am lost at what else to try other than to just going to another style booth or build me a homemade booth. I remember painting in an open shop when I was younger and had jobs as clean as what I am getting now.

Is it possible to modify a crossdraft to maybe a side draft with a little ingenuity instead of building an entirely new booth from scratch?
 
#2
I would be looking at airflow through the booth. Size of booth compared to CFM output of fans. Do you have both intake and exhaust fans?
Sounds to me like there is some turbulence in the booth, where air is swirling back over the fresh paint rather than exiting out of the booth.
 
#3
Make sure the seals on all doors, lights and seams (even the floor to wall) are not leaking air. You need just a little positive pressure to make sure you are not pulling in on the walls and seams, with a little positive pressure you are pushing air out any small leak not pulling air and dirt in.

In a perfect world you would have absolutely neutral pressure with an absolutely perfect seal everywhere but not all things are that way so I always recommend just a slight positive pressure for that reason.

This rule would apply to a booth with an air make-up unit. Do you have on of those? if not then make sure it is sealed everywhere and go in with a clean painter suit and also make sure the car is clean.
 

Chris_Hamilton

Trying to be the best me, I can be
#4
Another key area to look at and think about is the vehicle itself. In collision work you need to do what you can to clean the vehicle in the time you have allowed. Usually for me that just means a good rinse of the entire vehicle including underhood and all wheelwells. Limit or eliminate blowing off the vehicle in the booth. When you tape it up do it in such a way that you seal off everything that you are not painting. Meaning instead of using wheel covers, backtape and mask the entire wheel well opening. Idea is to seal off the dirt so when you are spraying the air doesn't push the dirt through. It works nicely for me. I paint in a dirty semi downdraft with seal issues, and I never buff. Usually just a single or two pieces of trash per job. Also I sweep very thoroughly before each job and leave the floor dry. I do like to wet the floor in front of the booth down and tape the tri fold doors due to seal issues.

I really feel that the vast majority of trash comes from the vehicle itself. If you can't get it clean then you got to tape in such a way so that the dirt can't escape from the various cracks and crevices. Blowing off a vehicle in the booth is a big no no IMO. If you got to blow off do it before you pull the vehicle in the booth, only tack once inside the booth.

It really boils down to thinking about everything you are doing. Wear a quality shoot suit, be aware of how you position the car in the booth, If you are doing one side, position it on the opposite side of your entrance door. If you are like me you go in and out and that can be an issue. Also look at your hose, keep an old tack rag in your hand as you shoot and keep the length of hose you hold in your hand clean. Blow yourself off before putting on your suit and when you walk in the booth. Tack before sealing, after sealing, at least once during basecoats, and finally before you shoot your clear. If you have the luxury of doing so, try to shoot when shop activity is at a minimum. If not tack more frequently. Like I said it's a combination of many things and not always the things that you think it is.
 
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#5
I don't wet the floor but I do use Devilbiss floor trap in a bug sprayer on important jobs. It seems to help. I'm with Chris in most of the dirt comes from the vehicle.

In a perfect world we would all have positive pressure air makeup booths but thats not gonna happen. Although I've seen some really dirty stuff come out of our local body shop with a full downdraft. Probably coming from the vehicle itself though. They don't wash anything.
 
#6
yes most trash come from the vehicle or you. a new spray suit, tack off the last 5 ft of air line. crossflow booths are all vacuum so nothing you can do about that. be sure you have good intake filters, nothe cheap green or blue ones with the glue sprayed on them.you can buy higher quality ones like airflow research afr-1. they work so much better. be sure the booth is sealed up good, turn the fan on 20 min before you enter the booth to tack off. leave the fan on the whole time until you are done spraying.
 
#7
Gotcha thanks guys. I will keep working at it. I do wear a paint suite as well. I try my best to keep vehicles clean and i do backtape and mask all the wheel wells. But I have never measured my airflow. This could be an issue. The filters I have been ordering are Viledon filters. Luckily, I only do this part time now so I am only painting a couple cars per month, but it does get very frustrating to have a nice slick paint job that requires extra time to sand and buff due to trash.
 
#8
I heard a guy say that he sprays the masking first from a distance that won't cause a disturbance but close enough to have the spray lock down the loose particles.
 
#9
I work in a homemade cross draft booth and often much of my body work is done there as well. For me what works best is all of what Chris said above plus I completely clean the booth by hosing everything down with water. I mop the floor and then wash the vehicle completely outside before bringing it back in to the booth. Sometimes I wash the vehicle in the booth while cleaning the booth at the same time. Yes, it is a lot of steps but when you don't have a separate area for all the block sanding, the dust is in every nook and cranny and seems to find it's way into your otherwise perfect paint job.
 
#10
I noticed yesterday that the seals around all of my light fixtures are foam and they are old enough that they are starting to break down and come apart. I can actually see pieces of the foam coming off and settling in the bottom of the fixture windows. I am thinking that my foam seals are part of the problem. I am going to replace all of the seals on my doors and light fixture windows with rubber seals to see if that helps.
 

Barry

Paint Fanatic
Staff member
#11
This will not be an easy fix but trial and error.

First thing is Green masking paper and brown will cause this problem, use only coated paper.
You have a suit, make sure you have a head sock.
DON"t wet floor, dirt doesn't come from floor and the water can cause dirt to "pop up in clear"
Now do a side or front end with booth drive in doors open.
Just a start.
 
#12
It is funny you mentioned green paper. I notice a huge difference in the amount of trash with green paper vs coated paper. I only use coated paper now.
 
#13
Where do you guys buy your intake filters? I did a quick online search for airflow research afr-1 and didnt come up with much. Decent intake filters would be a big improvement for me.
 
#16
Thanks Jim. On average how long would you say this type of intake filters last? 1 car, 2, 3? Its kind of a loaded question depending on the environment they are filtering. Just kind of looking for an idea as I have no clue what to expect.
 
#17
it all depends. mine seem to go every 2 changes of the exhaust filters. really depends on how much you spray and how dusty the air is going through the filters. you will get far more than 3 cars. i change mine maybe every 3 mos.
 
#18
That's what needed to know. I'm not doing anywhere close to a large amount of painting, 1 vehicle for the foreseeable future. So if I can come up with just enough for 1 change to good filters I would be good to go.