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[oldiron]

PAINTING SAFETY

  This issue of our discussion is about painting safety. Its something talked about among modelers from time to time, but not often practiced. We tend to get into the thrill of the build and tend to overlook the hazards we are dealing with because “we are only using a little bit” “for a short time”. Quantity and length of exposure certainly are defining factors in what happens to our bodies when we uptake a chemical hazard. However, the type of hazard is very much an important factor too. Here we will discuss some of those hazards and how we can control them and reduce the risk involved.
  We use a wide variety of different chemicals in our desire to create the latest and greatest. I’m no different than the rest. We get into lacquers, cyano acrelates,  enamels, fumes created from such things as soldering and from  resins when building hulls to name a few. In much of this work our exposure time is short, however, depending on how many models we build the effects can build over time.
  Lacquer paints are probably among the worst we deal with on a regular basis. This is because they contain VOC’s (volatile organic compounds). These compounds make up such chemical compositions as aliphatic hydrocarbons, ethyl acetate, glycol ethers, and acetone.   Granted many of us have switched over to water base paints, however, I’m one of the hold outs because of the finish, cover ability and durability compared with other types of paints. With that in mind here is a write up of the effects of lacquer based paints from the Sherwin – Williams paint site:

Section 5 — Health Hazard Data
ROUTES OF EXPOSURE
Exposure may be by INHALATION and/or SKIN or EYE contact, depending on conditions of use.
Alcohols and acetates can be absorbed through the skin. Follow recommendations for proper use,
ventilation, and personal protective equipment to minimize exposure.

ACUTE Health Hazards
EFFECTS OF OVEREXPOSURE
Irritation of eyes, skin and respiratory system. May cause nervous system depression.
Extreme overexposure may result in unconsciousness and possibly death.
Headache, dizziness, nausea, and loss of coordination are indications of excessive exposure to vapors or spray mists.
Redness and itching or burning sensation may indicate eye or excessive skin exposure.

MEDICAL CONDITIONS AGGRAVATED BY EXPOSURE
None generally recognized.
EMERGENCY AND FIRST AID PROCEDURES
If INHALED: If affected, remove from exposure. Restore breathing. Keep warm and quiet.
If on SKIN: Wash affected area thoroughly with soap and water.
Remove contaminated clothing and launder before re-use.
If in EYES: Flush eyes with large amounts of water for 15 minutes. Get medical attention.
If SWALLOWED: Urethane Retarder => Get medical attention.
Other Products => Never give anything by mouth to an unconscious person. DO NOT INDUCE VOMITING. Give conscious patient several
glasses of water. Seek medical attention.

CHRONIC Health Hazards
Carbon Black is classified by IARC as possibly carcinogenic to humans (group 2B) based on


  How do we adequately protect ourselves from these hazards? Proper ventilation and wearing breathing protection is the best. What we don’t want to do is limit ourselves to a confined space where the toxins can accumulate while we breathe. Some of us spray outdoors with no other protection. A good start, but wearing some additional breathing protection would be a whole lot better.
  What about spraying inside our shop? After all we can’t always wait until the next sunny day to unleash our artistic talents through an airbrush. I know of at least one chap told me he had a spray booth. When I looked at it I was shocked. He was spraying directly into an unventilated cardboard box. I reminded him about the hazards and how he was magnifying them through his painting method. He brushed it off as fine. A few years later he was pulling an oxygen bottle around; I don’t think he’s alive now. The word is be wise and be careful.
  For many years I’ve used a ventilated paint booth that I built. I constructed it from plywood. I didn’t have any dimensions to go by, so used some test ideas to come up with what I have. I tried to keep the box as small as I could reasonably do and allow me comfortable access to the inside with some fairly large pieces. I went to my local hardware store and bought the biggest kitchen ceiling fan I could find, to shift the most amount of air. I also made sure it had a spark less (or brush less) motor drive. The sparkles or brush less motor is required due to the volatile nature of paint fumes. Lacquer and oil based paints being the worst. The sparking of the motor brushes, during operation, can cause the fumes to ignite rather violently when painting.
  I have the fan in the top of the fume hood, more due to my circumstances. The fan could be mounted under the fume hood to produce a downdraft type of paint booth. The fan was exhausted to the outside of my workshop. When I had it assembled and tried it, I lit a candle and, with the fan running, held the candle in the box opening to see the draft effect. The candle flame was drawn into the box indicating the draft was working as desired. I have no way to measure the air movement by volume. However, I haven’t run into a circumstance of smelling paint outside the paint booth.
  With this design I can put most of my modeling work inside the booth and spray with a reasonable expectation of the fumes exhausting to the outside of the workshop. I took advantage of the paint booth structure to add a paint rack on one side and put my moisture trap on the other along with an electric power bar.
  There are many commercially made paint booths on the market that will do as advertised. If you wish to build one according to plan you can try these web sites:

http://modelpaint.tripod.com/booth2.htm

http://pages.interlog.com/~ask/scale/tips/booth.htm




My paint booth. The fan is the grey portion on top. The stove piping vents the booth up a spare chimney in my house.




This picture shows the paint rack I made for one side of the booth. Keeps the most commonly used paints close to hand.




  As an additional breathing protection, I recommend an air mask. One that you can change the filtering arrangements on is best. That way you install charcoal filters when spraying oils or organics and fiber glassing resins, and use a mechanical filter medium for those times you’re doing sanding on your hulls. Pick a design that covers your nose and mouth comfortably and allows you to interchange the filtering medium by unscrewing the cartridge for replacement.
  Both the mask and hood should look after your breathing needs adequately. Don’t forget that VOC’s can be absorbed through the skin, so some sort of hand protection is advisable. This all sounds like a lot, but it will save you a lot of grief later in life.

John

[tt1]

Hello John, thanks again for a very comprehensive tutorial.  Re your spray booth I can fully understand the logic in mounting the extract fan above the filter hood, but could you explain a little more regarding, quote, "The fan could be mounted under the fume hood to produce a downdraft type of paint booth." In my ignorance I would of thought that this would be the last thing you would want while spraying - you'll no doubt have a logical explanation - (just had to ask!)    Also what type of filter is in the hood and how do you monitor the need to change/replenish?
          This is great stuff, looking forward to the next installment.    Regards, Tony.

[oldiron]

Hello John, thanks again for a very comprehensive tutorial.   Re your spray booth I can fully understand the logic in mounting the extract fan above the filter hood, but could you explain a little more regarding, quote, "The fan could be mounted under the fume hood to produce a downdraft type of paint booth." In my ignorance I would of thought that this would be the last thing you would want while spraying - you'll no doubt have a logical explanation - (just had to ask!)   Also what type of filter is in the hood and how do you monitor the need to change/replenish?
          This is great stuff, looking forward to the next installment.    Regards, Tony.

  Tony:

  Thanks for the kind comments, glad you're enjoying the article.
  In the commercial painting industry (cars and trucks and so forth) down draft spray booths are the in thing for the best paint jobs. There are a couple of reasons I know of. One, the air flow is moving downward aided by gravity. This is a good thing since it helps the air movement. The other is it draws all dust and dried paint particulate from the bottom of the paint job and doesn't let as much land on top of the paint job as would happen with my type of booth. Variations on the downdraft design are side draft. In this case the air flows in and out through the side walls.
  Personally I've not seen the benefit of down draft booths in my application. Since I paint in a basement, I have to pump the air upward to get it outside. Any advantages due to gravity are lost in this set up. On the other hand, if you're set up in a back shed where you can vent straight out the side of the building without having to raise the exhaust air column to get outside, you may see an advantage. As to dirt, we want to keep the painting area as clean as possible, but in our shops that is much more controllable working by ourselves than it would be in a commercial body shop.
  This leads us to filters. I don't use filters on the exhaust. The biggest reason would be to protect the fan from paint build up, and that does happen over time if you paint enough. Fully enclosed paint booths have a filtering system for air coming into the booth for obvious reasons. Since I don't have a fully enclosed booth, its difficult to filter the air coming into the booth, as you can imagine. If you do decide to put a filter on your exhaust, i would use furnace filters that we have over here. They're cheap and very common and can easily be replaced. You are going to suffer something in air flow when you do it. As to when the filter gets plugged? I can tell a lot by the sound of the fan. Sort of like the hose on your vacuum cleaner getting plugged. The fan motor slows down and gives a deeper growl......same thing with the vent fan.

  One thing I neglected to put in my comments was "light". I can't stress how important light is when painting, particularly dark colours.  There is the obvious brightness so you can see, but there is also the type of light you're using. For example, fluorescent lighting will alter the tones of colours. Not good when you're trying to mix up a specific colour. Paint the object, then wonder why its all wrong when you bring it out into the daylight. Look for daylight balanced lighting bulbs. It'll save a lot of grief if you're concerned about the colour of your model.

John

[tt1]

Brilliant, thanks John,

[Martin (Admin)]

Hi John,

Great stuff!

What about the use of non vented / filtered cooker hoods?
Although I guess not as good as a ducted hood, would it be of any use where I don't want to knock a hole through the house wall?

[dodgy geezer]

What about the use of non vented / filtered cooker hoods?

They will get rid of particles, but I don't think they are so good for gases. Even if you use activated charcoal filters, which are meant to adsorb gases. So if you are worried about the effects of breathing in volatile solvents they will not help much, but they will tend to trap paint particles. Not very well, because they are not working in a box-like structure, and you will tend to end up with little paint dots all over the bottom of the hood, which might annoy SWMBO. 

I also expect they will swirl the air in the room, which might end up with more gunge on the surface of the workpiece....

[oldiron]

 
  Martin
Dodgy has put the answer to your question very well.

John

[nige2307]

Hello John, thanks again for a very comprehensive tutorial.  Re your spray booth I can fully understand the logic in mounting the extract fan above the filter hood, but could you explain a little more regarding, quote, "The fan could be mounted under the fume hood to produce a downdraft type of paint booth." In my ignorance I would of thought that this would be the last thing you would want while spraying - you'll no doubt have a logical explanation - (just had to ask!)    Also what type of filter is in the hood and how do you monitor the need to change/replenish?
          This is great stuff, looking forward to the next installment.    Regards, Tony.

Another reason for having downdraft over top mounted extraction is as the spray rises the particles may form together and then become too heavy 4 extraction or collect dust particles and do likewise, both been detrimental to achieving a good finish.  Another less important yet usefull feature is as the fan and filter are beneath the booth , maintenance is easier.

http://modelpaint.tripod.com/booth2.htm    this explains better than i can... hope it helps

[oldiron]

Another reason for having downdraft over top mounted extraction is as the spray rises the particles may form together and then become too heavy 4 extraction or collect dust particles and do likewise, both been detrimental to achieving a good finish.  Another less important yet usefull feature is as the fan and filter are beneath the booth , maintenance is easier.

http://modelpaint.tripod.com/booth2.htm    this explains better than i can... hope it helps

  I agree. That is what I was trying to point out with : The other is it draws all dust and dried paint particulate from the bottom of the paint job and doesn't let as much land on top of the paint job as would happen with my type of booth.

  The maintenance feature on our small units becomes a mute point, however, on large industrial units I take your point.

John

[Tombsy]

Great info! Looking forward to more.

I thought I would share my experience spraying Klass Kote epoxy paint on my JAE rigger. It was sealed with 2 coats of West Systems epoxy and sanded with 220. This is my first try spraying epoxy paint and I started with the fast acting white primer. When you mix the 2 parts you do not have to wait the 30-40 minutes to activate like the other colors. I first tried the little Hobbico spray gun from Tower Hobbies but I wasn't very happy with it, I think the air pressure was too high and the paint was drying before it hit the work surface making it really gritty and dusty.

Yesterday I tried my Paasche VL with a #5 needle and tip and a bottle attached. I set the pressure at 20 psi (actually the same Mastercraft compressor you have, you have to love Crappy Tire).
I thinned it with 2 parts reducer and strained it through a paper paint filter. What a difference, it sprayed really well, no clogs and the surface dried silky smooth. The primer also seems to sand very easily. On to color next and maybe some flames if I can figure out the masking order. I shouldn't have to clear coat with the glossy colors unless I want to seal some decals.

I'm trying Klass Kote to stand up to the 60% nitro in my fuel, otherwise I would have to use auto clear coat and that would take a bigger compressor and an auto touch-up gun.

Again great job keep up the good work.

[oldiron]

Tombsy:

 Thank for the tips. Yeh, where would we Canadians be without Crappy Tire. I can hardly wait for the sales fliers each week.
Another paint, designed for models, I've found stands up to chemical abuse very well is Scalecoat. Applies beautifully, glass coat and stands up to heat and volatile chemicals with no problem.

http://www.weavermodels.com/page7.html

John

[CanadianTired]

Hi John

Thank for sharing your knowledge on airbrushing - it's certainly very useful to me! I notice you live in Ontario and wonder if I could get some advice from you? I have recently relocated to Canada and am just starting out on model boat building. Thing is I am finding it difficult to find sources of kits, tools (including airbrushes) or materials in Canada. Also despite searching the web I have not managed to find a model boat club anywhere near me. Do you buy from the US or are there any places in Canada that you can recommend? It seems that businesses in the US will generally ship to Canada, except for certain liquids. Would appreciate any pointers.

Andy

[chersguy]

Hello Canadian Tired (great username btw) welcome to Mayhem. There is a model boat club right in Hamilton, the Confederation Marine Modellers. They meet second Tuesday of the month, 7:30, at the Steam Museum on Woodward Ave. They also sail at the pond at Spencer Smith Park every Thursday in the summer. They're a great bunch of guys, very helpful to us newbies, and you'd be most welcome. Check out their website for more information. You should be able to find it on the "Clubs" listing in Mayhem as well. Hope to see you there.

[oldiron]

Canadian Tired: (yes a great handle!). Welcome aboard.
  Chersguy has given some good advice. I know some of the Confederation chaps, and they're a good bunch. Every year there is a Great Lakes Model Boat Expo in Kitchener, not far from you. Its a two day event and a great place to meet other clubs. Here's a link to that and other club URL's: http://www.metromarine.org/links.html
I'm in the Kawartha Marine Modelers.
 As far as air brushes are concerned, I get my supplies at a locla hobby story here in Lindsay (Hobbies and Beyond: http://www.hobbiesandbeyond.ca/). There are good hobby storees in your area two that should carry your painting needs: http://www.google.ca/#hl=en&biw=1440&bih=732&q=burlington%2C+ontario+hobby+stores&aq=f&aqi=&aql=&oq=&fp=19e974be687f7f6e

Hope this helps.

John

[CanadianTired]

Thanks chersguy and oldiron. Lots of good links there for me to look into, and I'll get myself along to the Confederation.

[grayone]

Is this post going to cover the surface prep prior to air brushing for the various materials we make our models from, such as GRP, that vac moulded plastic and wood?

[oldiron]

Is this post going to cover the surface prep prior to air brushing for the various materials we make our models from, such as GRP, that vac moulded plastic and wood?

  yup, I',m going to be looking at surface prep.

John

[oldiron]

PAINTS

  When we look around for choices of paint to decorate our models, we are barraged with a host of options. What is the difference between them? Which paints are best for my model? How do I use them? These and a host of other questions come to the fore.
  I will attempt to add some clarity to the puzzle. For those who have painted for some time I expect you will already have your favourite paints, however, this may open up some new ideas to you for future projects.

TYPES OF PAINT

The following is a list of the most commonly used types of paints
Acrylic
Enamel
Oil
Laquer
Water colour

  You can find most of the above types of paints available from many suppliers labeled for “model use”. What does that mean? It largely comes down to the size of the pigment in the paint. Model paints have very finely ground pigments. This aids in the covering (opaqueness) and the ability to pass the paint through the close dimensions of an air brush tip. Paints traditionally used for covering vehicles, our lawn furniture or the side of the house have much heavier pigments. The paint is being applied, relatively, thicker with a much courser application tool. Because the paint goes on thicker, the course pigments can build up and cover satisfactorily. With our models, paint applications are in the order of a 2 – 3 thousands of an inch thick. Larger pigments would look like golf balls and leave translucence to the paint that we would find unsatisfactory.
  Because of the larger pigments, in non model paints, we are hindered in our ability to thin the paint sufficiently to go through an air brush and, at the same time, hold the paint pigments together. Over thinning results on a less than durable finish. Because of the finer pigments in model paint we can thin the paint to a much greater degree before we see paint detereation. This characteristic makes model paints ideal for putting through an airbrush and making “washes” to weather our models.


ACRYLIC

  Acrylic paint is pigment suspended in a plastic suspension material know as acrylic polymer emulsion. The amount and type of emulsion can be varied to change the thickness of the paint, depending on the effect desired.
 This paint characteristically is fast drying and is easily cleaned up with soap and water. However, once set it is impervious to water. I like it for weathering. It can be thinned with water and used as a wash to great effect.  This paint can also be used through an airbrush when appropriately thinned.
   Tamiya (http://www.tamiya.com/english/products/list/acrylic_1.htm) is one of the manufacturers of this type of model paint. I’ve used their paint through an air brush and a bristle brush. It covers well and leaves a nice finish. Cleanup is easy with soap and water providing you don’t let it set up.




A selection of acrylic paints I use.

ENAMEL

  Enamel paint, in the traditional recipe, comprises of pigment held in an oil based carrier. Enamels used to be thought of as glossy finished; however, matte finishes have been developed that have put that description to rest.
  These paints tend to be durable and hard wearing, a good feature for models that get regular handling.   They are slower drying than acrylics and need to mineral spirits (or similar) for cleanup. They can be air brushed successfully. Humbrol paints recommend 2 parts paint to 1 part thinner as a starting point.
  My experience with Humbrol has been limited due to availability and those small cans over here. I find bottled paint , such as Model Master (Testors) produces, to be much easier to get the paint out of and its in reasonable quantities.
  Testors paints tend to be more available on this side of the pond and they produce a full range of different types of paints: http://www.testors.com/category/50736/Paints
  I’ve used the Floquil range of paints for many years. They are very popular with model railroaders : http://www.testors.com/category/133504/Floquil




Oil

    This paint consists of pigment suspended in a linseed base or similar drying oil. They are extremely slow drying. Their consistency is very thick. Because of these traits they are unsuitable for air brushing, but are ideally suited to artistic paintings such as done on canvas.

LACQUER   

  This paint tends strike fear into the hearts of many modelers. I’m not sure why entirely. Possibly because of the chemicals involved, however, correct ventilation and breathing protection looks after that.
  Lacquer is pigment suspended in a base of solvents typically consisting of butyl acetate and exylene or toluene or, in older lacquers some sort of volatile organic compound. Non of these chemicals are pleasant to the smell or the lungs. However, properly used they produce a durable fast drying finish. These paints can be baked on at up to 200 deg F. to produce an extremely durable finish that is impervious to almost anything.
  Model paints of this type spray beautifully and can leave a glossy finish ideal for wet transfer decal application (we will cover this later).
  Lacquer also has the downside of being hard on plastics. I’ve air brushed plastics without a primer or shield between the lacquer and the plastic successfully. The trick is to make very light passes to allow the solvents in the lacquer to flash off very quickly. Once this layer is on, the surface can be painted as one normally would. One advantage of doing it this way is the lacquer partially eats into the plastic giving the paint tremendous adherence power to the plastic surface.
  Tamiya has released a lacquer that is designed to go on plastics without harming them. It’s a synthetic based lacquer that covers beautifully, and is very fine grained. The only drawback is I haven’t found it in a jar as yet. It comes in spray cans, which makes it difficult to get into air brushes. With this paint a primer is recommended.
  I’ve used automotive spray paints, from rattle cans, for large surfaces such as hulls. Although they do have a larger pigment than model paints, the large surface being covered compensates for this. Also it’s not going through the fine confines such as an airbrush.



WATER COLOUR

  Water colour paints consist of a pigment in a water based carrier. The pigment grains tend to very course. This combined with slow drying and lack of durability make it unsuitable for most of the work we do. This paint can be mixed to make a stain that may find its use in staining handrails and so forth. By and large it is not likely to find a use on many of our models.  Poster paint and tempra paints generally fit into this category. Acrylics can do the job much better.

  When mixing paints don’t try and mix paints outside of their family of chemicals. For example don’t mix lacquers with enamels or acrylics. Enamels can be mixed with oils usually successfully.
  Although we have covered pigment paints, when painting an object it is usually wise to prime the object before hand. Pick a primer that is compatible with the paint you want to put on top. Any other way can result in major disappointment and a major re allotment of time to recover what you’ve done.
  As well as coloured paints, many of the manufacturers sell clear coats in gloss or matter finish. This is ideal for sealing in decals on a finished surface. We’ll cover that later.


John

[Martin (Admin)]

Found this on ebay...

SPRAY BOOTH + EXTRACTOR FAN FOR AIRBRUSHING.
http://cgi.ebay.co.uk/SPRAY-BOOTH-EXTRACTOR-FAN-AIRBRUSHING-/300419175584?pt=UK_ToysGames_ModelKits_ModelKits_JN&hash=item45f260d4a0

[oldiron]

Looks like a nice compact unit Martin. I wonder what they use for a medium for getting rid of various noxious vapours that are in many paints? You would usually need a carbon filter of some type. i ask because I don't see it mentioned in the write up. Just something to think about.

John

[tbone]

Great thread so far, lots of good info.
I was just looking at the Tamiya paints and they come in 10 and 23 ml sizes.  (They also offer thinner but I've heard people have used other things to thin the paint for spraying)
How much paint is needed to paint a hull or superstructure?  I'm sure the airbrush would use less than brushing but would one jar be enough?
Hull size matters, so roughly a 36" hull for examlple.

Thanks

[oldiron]

Great thread so far, lots of good info.
I was just looking at the Tamiya paints and they come in 10 and 23 ml sizes.  (They also offer thinner but I've heard people have used other things to thin the paint for spraying)
How much paint is needed to paint a hull or superstructure?  I'm sure the airbrush would use less than brushing but would one jar be enough?
Hull size matters, so roughly a 36" hull for examlple.

Thanks

 Ii believe the Tamiya paints you've indicated are acrylic. That being the case, Tamiya says it is water soluble, therefore, you should be able to use water to thin it with success. I've also tried methyl alcohol with success. Based on thinning the paint to 2 parts paint to 1 part thinner, I would guesstimate the larger (23Ml) size will do the hull you suggest. Normally you would say spraying would take more paint than brushing, but in the case of an air brush you are can make a smaller controllable cone of paint when spraying. This allows you to more accurately cover the object with minimum wastage and get a better finish than you could get with a brush. Don't forget, all paints don't lend themselves to brushing well. Some can flash to quickly to allow the paint to flow together after a brush has passed through it. This leaves the infamous brush strokes in the paint. Also paint tends to go on thicker with a brush than with an airbrush.
  As a side note, I found a web site that gives conversions of colour from one paint manufacturer to another. Can be quite handy if you find the colour you want, but want that colour from your favourite manufacturer.

http://www.paint4models.com/

John

[tbone]

Thanks John.  I assume the acrylic paint would have the least fumes, being water based?  It's been a while since I used tamiya paint but do remember getting good results with it.

Tbone

[oldiron]

Thanks John.  I assume the acrylic paint would have the least fumes, being water based?  It's been a while since I used tamiya paint but do remember getting good results with it.

Tbone

  Yes, being water base they are the most "fume friendly" you might say. I like Tamiya paints. They cover well and give a nice finish.

John

[dougal99]

I have tried thinning Acrylics with water but have had problems with surface tension ie the paint tends to form drops on the plastic surface ( I had previously cleaned the surface with surgical spirit). I tried thinning using car windscreen wash, with some some success, but plain water gave me problems. I have always used Tamiya thinners with their paint. Unfortunately, for my current project I couldn't get the colour I wanted so had to use Revell, which is not acrylic.