Material Safety and Model Railroading
A hobby shouldn’t hurt you. But while most people are aware of the dangers of power tools or sharp knives, there’s a tendency to believe household chemicals are “safe” as long as you don’t eat them, and that’s unfortunately not always true. This page collects information on some of the problem areas I’m aware of, but I make no claim that it’s complete. When working with any chemical, it’s worth doing a little research online to see what the known hazards are. And it’s better to trust an authoritative source if you can find one, rather than the “conventional wisdom” of many online forums. I’ve seen a number of “X is safe” postings, when the Material Safety Data Sheet (MSDS) lists a number of hazards; “Not immediately harmful” is not “safe”.
I’ll note that I’m neither a doctor nor a toxicology expert; this is merely information I’ve collected online for my own safety, which I’m posting here for my own reference and as a starting point for others. Don’t take anything here as certain, as I may have missed other documentation, or misunderstood what I found.
It’s worth noting that MSDS are typically written for the industrial user, and assume long-term frequent exposure. That doesn’t mean that a casual user should ignore the advice given. In particular, some people are more sensitive to certain toxins, due to past exposure or other reasons. And some of these chemicals are very toxic. Others will have a cumulative effect over the long term even for relatively small exposures. But you don’t need to be scared off either, as long as you take basic precautions.
Basic Chemical Safety
There are a few basic precautions to take when working with hobby chemicals, whether you are painting, gluing, or using resins (for casting, modeling water, or whatever). Those are:
- Ensure the room is well ventilated, and leave immediately and find fresh air if you get a headache or feel light-headed.
- Wear good rubber gloves (neoprene or nitrile gloves are generally preferred; latex gloves are porous to some chemicals).
- Wear glasses, preferably safety glasses with splash screens on the side, to protect your eyes against droplets.
- Don’t eat (or smoke or chew your pencil) while working with chemicals.
- Don’t store or use flammable chemicals near an ignition source (e.g., a furnace, gas hot water heater or dryer, etc).
- Wash your hands with soap and water after you finish, even if you were wearing gloves.
These basic precautions (particularly good gloves, safety glasses to avoid spatter, and good ventilation), should make most of the commonly-used hobby chemicals relatively safe to use. Understand the various chemicals, treat them with the same respect you’d give a power saw, and you should be okay.
Note: According to the EPA, the disposable “nitrile” rubber gloves sold for automobile maintenance are a “good” (not perfect) glove for use by automobile painters against paints and organic solvents. Many of the problem chemicals encountered in model railroading are also organic solvents, so the advice applies to us as well. Butyl rubber gloves are better, but aren’t as flexible, and in most cases nitrile will likely be good enough, particularly for the casual level of use common to most hobbyists. Latex gloves are porous to some chemicals, and generally not a good idea, even if you aren’t allergic to them. Even Nitrile isn’t perfect, as the EPA notes some chemicals, including MEK (a solvent used with some hobby glues) will pass through Nitrile.
Safety Glasses
I can’t emphasize this enough: wear something to protect your eyes! That’s the single most fundamental safety precaution. Even ordinary glasses are better than nothing, but real safety glasses that will protect from splashes are much better when working with any liquid chemicals. While prompt washing may be enough to prevent permanent damage in the event you get something in your eye, that won’t always be true. Some chemicals are going to cause immediate, and permanent, damage.
Respirators
There are a number of different kinds of respirator. The simple cloth one held over the nose and mouth with an elastic will block a large percentage of particles, but it doesn’t make a complete seal and it won’t block chemical vapors. This is something to wear when cutting lumber or XPS foam (both of which put a lot of dust in the air) or when working with a “safe” paint like latex.
But if you’re working with things like resins (for modeling water) or paints with organic compounds, it’s not going to provide a whole lot of benefit.
The better type of respirator is a “half-mask” made of rubber and plastic that covers the nose and mouth, and provides for attaching filters (which can be purchases separately). This is known as a Reusable Respirator, and they can be found in paint and home improvement stores. The better ones allow for both a filter cartridge that deals with vapors (several kinds exist) and an external particle filter that looks like a cotton pad. Often when painting, the particle filter will need to be replaced more often than the cartridge (consult the manual that comes with the mask, or instructions packaged with the cartridge). I use one of these, which takes 3M 6000-series cartridges; these appear to be very common.
With this kind of respirator, making a good seal against the face is necessary for it to function properly, so following the instructions to do so and verify that it is sealed is important.
The following information is U.S.-centric, as every country will have their own health and safety regulations affecting these kinds of masks, which will define what’s available for use.
Current U.S. standards for passive (also known as “air purifying”) respirators are based on “42 CFR 84”, which identifies filters as being one of three types (N, R or P) and with an efficiency rating based on the percentage of particles they remove expressed as a two digit number (e.g., “P95”, for P-type, 95% removed). Note that a P100 filter doesn’t actually remove 100% of particles, but 99.7% per the standard.
In 1999 sale of respirators conforming to older standards was prohibited in the U.S., and all must now conform to the revised standards from 1994. This may not make any difference in practice to a modeler, but if you have a really old respirator, you may want to update it with a new one (I did, but mainly because I couldn’t get filter cartridges for the old one anymore). The National Institute for Occupational Safety and Health has a page about respirators, although it’s rather technical and doesn’t say much relevant other than “if you don’t have airborne oil or similar particles, all three kinds of filter type, N, R and P are acceptable.” However since “oil” can mean any of a large number of airborne liquids, use of a “P” filter is probably best.
The kind sold in my local store couples a P95 particle filter (oil-resistant, removes 95% of particles) with an organic cartridge (which is basically just an activated carbon filter). This should be useful against nearly any substance you’d encounter in modeling or layout construction, other than ammonia. However, I have not exhaustively checked every substance I use. Ammonia, which can be given off by some substances “curing”, requires a special ammonia filter in place of the organic vapor cartridge.
You can buy special “multi-gas and vapor” filter cartridges that protect against a variety of things, but these cost about twice as much and seem to me to be overkill for the kinds of substances I’ll encounter in my modeling work. I’d buy a set of these if I were going to be working with any ammonia-producing substances, since they’ll work for both that and organic vapors.
Instructions on when to change these (outside of commercial/industrial uses, which have much more specific requirements) boil down to:
- change the particle filter when it becomes clogged (i.e., when it’s harder to breathe through it).
- change the “gas/vapor filter” if you can smell anything through it, or once a month in any case.
Note that since many harmful chemicals don’t have any odor, the “when you can smell it” test may not be all that helpful.
Additionally, the “after 30 days” part doesn’t show up in all versions of the recommendations I’ve seen. In some it’s not mentioned at all, in others it’s given as “after 40 hours of use or 30 days”. I expect it’s really tied to how often the carbon gets exposed to substances it could bind with, and in hobby applications these are probably going to last a very long time.
Even so, replacement organic vapor cartridges can be had for less than US$10 (I’ve seen mine as low a $6 a set on Amazon), so replacing them periodically is a good idea. I tend to keep my organic cartridges in place longer than 30 days, but swap in a fresh set before beginning any large project with paint or other substances that would have organic vapors if it’s been more than a month since the last time. As long as you keep the bag sealed, spare sets should have a very long shelf life.
Wood and Other Particles
Any time you cut material with a saw or serrated knife, you’re breaking off small particles of the material that form dust. Dust of any sort is very bad for the lungs, and over the long term can cause may of the same respiratory problems that smoking does. Wearing at least a dust-mask, and preferably a respirator, is very important when cutting wood or foam. If you use pressure-treated lumber for anything, be aware that this contains toxic chemicals that will be present in any dust, making a good respirator even more important.
And cleaning up the dust afterwards is important too. Wood dust will tend to lie on the floor (or other surfaces) unless kicked up, but foam dust can pick up an electrostatic charge and float around the room for an extended time. I always run my shop vac when cutting foam, to leave the minimum dust in the room, and then vacuum up any I can see immediately afterwards.
A shop vac with a replaceable HEPA filter on the output (in addition to the normal filter protecting the motor from clogging) is very important for removing fine dust.
Gloves
Chemicals of any sort are usually bad for you even if you get them on your skin, as they can soak in and get into your bloodstream. Gloves are an essential protection when working with chemicals in any significant quantity, and a good idea otherwise. Even a reasonably safe compound like plaster is an irritant to skin (particularly before mixing with water) and using gloves with chemicals presumed to be benign is a good idea.
Thick gloves provide more protection than thin gloves, but are often not practical where dexterity is required (e.g., when painting a model). For modeling uses, often thin disposable gloves are both sufficient and provide little impairment of manual dexterity. For particularly dangerous compounds thicker gloves than the disposable kind are recommended, but avoiding such chemicals would be preferable.
For most chemicals, nitrile gloves (available in disposable form from automobile supply stores and home-supply stores in the paint section) are preferable to latex (and some people have allergic reactions to latex). However, there is one significant exception: latex is better protection against acetone (which is a component in super-glue solvents and thinners), although only if the gloves are relatively thick (i.e., not disposable latex gloves). For some chemicals neoprene or a neoprene-rubber compound is preferable, but these gloves are typically thicker and don’t allow for the kind of manual dexterity needed with small parts. For some things butyl rubber, not latex, is the best protection.
If working with MEK glue, thick butyl rubbers gloves appear to be recommended (but MEK will still get through it after several hours). Some use double nitrile gloves (throw them away after use, the solvent will slowly dissolve them). However I’ve seen others recommending against them, as they are permeable to it (i.e., it will get through before the glove visibly fails). Since MEK will happily dissolve skin too, it’s better to avoid using it at all, if you can. If not, wear gloves for splash protection and be careful not to get it on them.
Ordinary kitchen “rubber” gloves are usually latex (a type of natural rubber), but may also be made of Vinyl (also known as PVC), either of which is good for soap but very bad for most organic solvents (paint thinners, etc). Do not confuse latex rubber gloves with butyl rubber gloves (often recommended for use with chemicals) as they are different substances.
Latex and Other Layout Paints
Latex paint is relatively harmless, which is something that cannot be said of many older types of paint. Latex paint itself has “no known hazardous ingredients”. Still, use a respirator if working in a poorly ventilated area (or if using a paint sprayer), and an “impervious type” (i.e., nitrile) glove is recommended, as well as eye protection. Paint formulas can vary, so it’s worth looking online for Material Safety Data Sheets (MSDS) for the specific brand and type of paint you’ll be using. You can also get interior latex paints with a “low volatile organic compound” (or “low VOC”) formulation. These will not only smell less while the paint is curing, they’re better for you since those VOCs are the part of paint that’s hazardous.
Model Paints
Before we had different kinds of paint for models there was just “model paint”. This is now known as enamel paint. Most paints for modeling are of this type, and it can be assumed if nothing specific is said (there are also some hybrid paints that have attributes of both acrylic and enamel paints). Increasingly-common however are water-based acrylic paints. This is different from the acrylic paint sold for artists, since it uses finer pigment grains for coating models with small-scale detail. While enamel paint is probably no more hazardous than the glue used to put models together, that’s not exactly risk-free. Acrylics are water-based, and much safer, but still use thinners that have some risks.
Note: as a general rule, you shouldn’t mix different types of paint on one model. There are exceptions (enamels can usually cover acrylics, but not vice versa).
Airbrushing
Airbrushes create a fine mist of “atomized” paint particles. These don’t all end up on what’s being painted, and inhaling them is a really bad idea regardless of the chemical compound (fine particles in lungs cause all sorts of long-term health problems). Use of a respirator is recommended if you airbrush with any paint, even if you use a spray booth, although a well-designed spray booth certainly reduces the hazard posed by airborne particles. Use of safety glasses with side protectors (to keep paint out of your eyes) and gloves (nitrile or similar) is also recommended.
Airbrush thinner is usually some kind of organic solvent, so it should be treated as a hazardous chemical in its own right. As a fine mist from an airbrush, it’s generally also flammable and should not be used near an ignition source (like a furnace or gas stove with a pilot light).
Acrylic Paint
Acrylic paints used for painting models are often (but not always) water-based and relatively safe, but good ventilation and “impervious” gloves (and eye protection) are recommended practices. A Badger MSDS (Google for Spectra TEX) recommends use of a respirator, splash goggles, and “impermeable clothing and gloves”, but this appears to be aimed at airbrush use of such paints. It otherwise describes them as non-flammable and noting only that “prolonged contact may result in mild reaction in some cases”.
This varies by brand, with some brands using a water/alcohol or even stronger solvent as a medium. You need to check for an MSDS for the specific brand of paint you want to use.
Both Tamiya and Model Master acrylic are said to use alcohol in their thinners. I haven’t verified this.
Note: even if acrylic paint is thinned with water, airbrushing use of acrylics often uses other thinners, such as Isopropyl Alcohol. These are often flammable, so airbrushing near an ignition source (e.g., gas appliances such as a stove with pilot light, hot water heater, or furnace) can be hazardous for reasons completely unrelated to the chemical composition of the paint. This varies a lot, so try to find an MSDS for your specific thinner if you can.
Testors Model Master Universal Acrylic Airbrush Thinner (Testors MSDS) is relatively safe. They recommend “splash goggles” and “solvent resistant” gloves, but only “good room ventilation”, and there are no other hazards listed beyond a slight risk of developing an allergic skin reaction from chronic repeated exposure (hence the “use gloves” recommendation). It’s non-flammable.
Badger doesn’t provide an MSDS for their Spectra TEX acrylic airbrush cleaner, something that always makes me suspicious. Its noted as “not flammable when used as directed”, however one of the compounds listed is 2-butlyoxyethanol, which is flammable (as well as being rather toxic). It may be present only in a very small quantity, but absent an MSDS clearly stating that, I’d assume there’s a risk and treat it like an alcohol-based thinner.
Enamel Paint
Enamel paints are not as safe as acrylics: “overexposure” to fumes can cause not just irritation, but “central nervous system depression leading to headaches, nausea, dizziness and loss of consciousness.” (quoting a Testors MSDS). Long-term exposure to enamel paints may also cause liver, kidney and lung damage, and is a potential cause of “cancer and birth defects.” Keeping enamel paint off your skin (i.e, gloves and eye protection) is considerably more important than with acrylic paints. That all said, good ventilation and keeping the paint and thinner off your hands and out of your mouth (don’t eat or smoke while painting) should make these relatively safe.
Airbrush thinners for enamel paints tend to have the same hazards as the paint, in addition to being highly flammable. There’s an increased hazard of inhaling the chemicals though, since you are spraying them into the air. Good ventilation (open window or a vented spray booth) AND a respirator with fresh “organic vapor” cartridges are really good ideas here.
Lacquer Paint
Lacquer-based paints, like the older Floquil Railroad Paints, are extremely hazardous, causing permanent nerve damage with long-term exposure (they’re also carcinogenic). That’s probably why Testors changed the formula to an enamel paint when they acquired the product line. If you have any of the old stuff lying around, I’d recommend disposing of it (safely, though a hazardous materials collection site; this is not stuff you want in the water table) rather than continuing to use it. Thinner for this is similarly bad for you and the environment.
Expanded and Extruded Polystyrene Foam
The Woodland Scenics white polystyrene foam sheets and other “SubTerrain” elements are “expanded” foam (also known as “EPS”), and unlike the “extruded” foam (also known as “XPS”) used in pink and blue insulation, they claim there is no toxic gas released when their foam is cut with a hot-wire cutter. The implication is that other kinds of foam do have such emissions, although they may be referring to polyurethane foam.
The typical “insulation” foam panels, including Owens-Corning’s pink Foamular brand, are Extruded Polystyrene (XPS), which are basically gas bubbles trapped in foamed plastic which has been extruded, so the foam is easier to cut along its length. At present, the gas used is typically a hydrochlorofluorocarbon (HCFC), which is “relatively non-toxic” and harmless to humans in the small quantities released by cutting foam (it is bad for the ozone layer, however).
EPS or XPS insulation foam used in model railroads is mainly hazardous due to breathing in dust from cutting or drilling, although it can be irritating to skin or eye contact. Use of a respirator is recommended when doing anything that could generate dust (e.g., “crushing, grinding, drilling”). Long-sleeved work clothing and eye protection is also recommended. Gloves do not appear to be necessary (“no effects expected” from skin contact), but the MSDS for Corning Pink foam (which can be found through the Owens-Corning website, under Literature) recommends washing with mild soap and running water if irritation develops.
Actually burning polystyrene is quite hazardous, and this may be the risk Woodland Scenics is alluding to. Burning it produces “carbon monoxide, carbon dioxide, and styrene” as well as “hydrogen fluoride, hydrogen chloride, carbon monoxide, carbon dioxide, fluorine, and chlorine” decomposition products at high temperatures (likely only found in a fire, and not in a hot wire).
I have seen some online comments about outgassing, but aside from burning it, there’s nothing in the MSDS about airborne hazards other than dust from polystyrene foam. Polystyrene is a stable material, which does not decompose over time (unless exposed to ultraviolet light, e.g., sunlight). Urethane-based foams are a different matter, and this may be the root of some of the confusion in online posts about foam materials.
Polyurethane insulation foam does outgas fluorocarbon gas from the foam when new, and this decreases over time, with the bulk occurring within the first two and a half years after manufacture. Some older insulation foams (Urea formaldehyde foam, no longer made) outgassed Formaldehyde. Neither of these is really suitable for model railroad use anyway, although I’ve seen articles about using polyurethane foam as a scenery material.
Glues
Glue is increasingly common in model railroad construction. L-girder benchwork depends on a glue bond for its strength, and cork roadbed has typically been glued to the subroadbed with a common wood glue. But increasing use of polystyrene foam has made model railroads even more dependent on glue, and newer formulations make it easier to use glue where other attachments have been used in the past. Note that “white” wood glue, which is water soluble, is not recommended for use where it would be exposed to water during ballasting or other scenery work, as that could dissolve the glue.
We also use glues for models, typically “plastic cement” for polystyrene models. This stuff is a lot more dangerous than you’d expect of something often used by children, and needs to be treated with the same respect you’d give a power saw. Used carefully, it should generally be safe enough to use, but it can be quite harmful.
Wood Glues (PVA)
Traditional Wood Glue, or “PVA” (Polyvinyl Acetate) is a very safe substance. Wood glues, including yellow “carpenter’s glue”, which is what I use, are non-toxic while curing and afterwards (neither gloves nor special ventilation are noted as necessary on the Material Safety Data Sheets I found).
Having said that, I discovered that even PVA isn’t quite as non-toxic as I thought. Although it’s limited to “skin and respiratory irritation”, rather than the far more severe risks of polyurethane glues or some latex caulk (see below), and mostly an issue if you are working with heated (or vaporized) glues, there is some risk. See the MSDS for Tightbond glues, as well as Elmer’s Carpenters Wood Glue (although the latter appears less hazardous, it appears to me that this is merely a difference in presentation, and both say essentially the same thing: it should be safe under normal conditions). It’s still safe to touch, and in normal use fumes would not appear to be a concern, but they recommend washing hands after working with it, and seeking fresh air if eyes or nose/throat become irritated.
Other Glues for Wood, Cork and Styrofoam (Polyurethane and Latex Caulk)
Unlike bare wood, painted wood and styrofoam do not produce a bond “stronger than the wood” when joined with wood glue, as neither has open pores for the glue to penetrate deeply into the material. However, both have sufficient surface texture for the glue to attach, and both have fairly large surface areas in model railroad applications, so even though the bond is likely weak, it is sufficient to hold the material solidly together under any stress a model railroad is likely to experience. And besides, neither styrofoam nor cork is particularly strong anyway; there’s no need for the glue to be stronger than the weakest material involved.
If that isn’t sufficient, other glues may hold better. Polyurethane glue (one common version is Gorilla Glue) is non-toxic once cured, but can give off toxic fumes while curing and be dangerous to touch before it is set (latex, nitrile rubber or butyl rubber gloves are strongly recommended, in addition to a “well ventilated” work area). See the MSDS for Elmer’s Probond Polyurethane glue. Gorilla doesn’t seem to publish their MSDS directly, but if you Google around you can find copies with similar information.
Another glue often used in place of wood glue, particularly with styrofoam, is acrylic latex caulk, sold under a number of brand names, including Liquid Nails. However, there are many different formulations and not all are suitable for use with foam; read the labels closely. And, of course, the MSDS for each formulation is likely going to vary somewhat. The kind typically recommended includes silicone, which keeps the caulk flexible after curing, and helps to damp vibration when used for track and subroadbed.
You can find MSDS for some common brands (DAP, Liquid Nails) online. The “Low VOC” versions of these are still toxic, but contain far fewer airborne substances of concern (both in volume and in number of different chemicals).
When curing, even “low VOC” siliconized caulks can give off ammonia, ethylene glycol (antifreeze) and formaldehyde, none of which are good to breath, or to touch. If you use these, make sure to have good ventilation and wear gloves. Even “ordinary rubber gloves” are not sufficient protection (neoprene is recommended on one MSDS I saw, although nitrile gloves may be sufficient for most hobby use).
Since respirators (with an “organic vapor cartridge”) are only recommended if ventilation is inadequate, and other precautions typically amount to “wear gloves” and “wash hands and contaminated clothing after use”, this is likely reasonably safe if you take basic precautions. Much of this is probably of more concern to professionals who work with the substances every day, as opposed to hobbyists with casual and infrequent contact. But I don’t want to breath it in a poorly-ventilated basement, and if there’s a non-toxic alternative, why take the risk? I f you do use a respirator, note that you need more than just the basic organic filter cartridge, due to the presence of ammonia (see the respirator section up above).
Aleene’s Tacky Glue
Another glue often used in model railroad applications is Aleene’s Tacky Glue, a “water-based polyvinyl alcohol resin”. This is labeled as non-toxic, but can still give off hazardous substances while curing (likely in small amounts). The MSDS, which doesn’t seem to be published directly, but which can be found via Google, recommends ordinary ventilation and “chemical resistant” gloves as well as safety glasses.
This appears to be water-soluble, and thus inappropriate for track and subroadbed which would be ballasted, or for other scenery work where water or “wet water” will be used extensively.
Note: there are several different glues branded “Aleene’s”, and not all are as safe as the original.
Mod Podge (PVA)
This is a water-based PVA type glue (similar to white glue and Carpenter’s glue). Originally developed for decoupage (gluing dissimilar materials together for craft projects) it is a tacky glue that dries flexible. It comes in a variety of formulations today (MSDS not online from manufacturer, Google for “plaid mod podge msds” to find one).
The MSDS for the original Matte formula notes the usual cautions relevant to PVA, and further states that “As packaged for consumers, this product is certified in a toxicological evaluation by a medical expert to contain no materials in sufficient quantities to be toxic or injurious to humans, including children, or to cause acute or chronic health problems.”, which is one of the more sweeping statements I’ve ever seen in an MSDS.
There is also a “Paper” version of it (available in both Matte and Gloss finishes) which is non-acidic, and probably a superior glue for backdrop photos to the standard version, but I haven’t been able to find a MSDS for that type.
Special-Purpose Glues
A number of more exotic glues are used in specialty applications on or around model railroads. Some of these are “solvent” adhesives, meaning that they melt the material being glued and create a weld where the two parts are intermingled. This is a very strong bond, but depends on both being the same kind of material, usually plastic of some sort. Unfortunately, melting plastic requires some seriously dangerous compounds.
Cyanoacrylate (CA) Glue (SuperGlue)
As most people know, one of the big hazards of SuperGlue (a brand name for cyanoacrylate, or CA, glue) is that it can glue skin to skin instantly. Use of gloves and protective eyewear is strongly recommended for that reason, although the material itself is relatively non-toxic. The vapors are also an irritant, and good ventilation is recommended. Exposure of uncured glue to water, alcohol, or other substances may pose a fire hazard. See the MSDS for Krazy Glue or Testors Model Master Instant Adhesive for more detail.
I’ve seen reports that organic vapor cartridges on a respirator are not effective against superglue vapors, but I haven’t been able to find anything definitive. Good ventilation seems to be the best solution here.
CA is not appropriate for use on models that have transparent plastic windows, as the gas given off while it cures will cause them to fog.
MEK (Methyl-Ethyl Ketone)
MEK, also known as “butanone”, is a component of solvent-type glues used with plastics, particularly PVC. It’s also a component in lacquer thinner (which contains additional compounds). It’s fairly dangerous, although it may be less dangerous than toluene-based Polystyrene Cement. It’s often used in larger quantities though, which increases the potential exposure, and thus the risk.
The MSDS lists it as being an irritant (skin, eye and inhalation) and possibly toxic and warns that “repeated or prolonged exposure to the substance can produce target organs damage.” It’s also highly flammable. It can be absorbed through skin contact or the vapors breathed. Excessive exposure “may cause central nervous effects characterized by headache, dizziness, unconsciousness, and coma.” It may also be teratogenic (don’t use it if pregnant or around a pregnant person).
I’ve read of people losing skin to MEK exposure.
Recommended protections include: “splash goggles, lab coat, vapor [organic vapor] respirator, gloves”.
However, as noted in the section on gloves, thin nitrile gloves are somewhat permeable to MEK, and it will also dissolve them over time. So even when wearing gloves, exercise caution to keep it off your hands. A double-layer of disposable gloves may be a good idea when working with large quantities, or use of heavy gloves. Natural rubber is a better protector than nitrile (but be cautious, many “rubber” gloves are not made of rubber or may be a rubber/neoprene mix, which isn’t as good; check the fine print).
Polystyrene Glue (Model Cement)
Polystyrene (ordinary model plastic) is typically glued to itself using “model cement”, which is a toluene-based solvent adhesive. This stuff is pretty nasty. It can be absorbed through the skin, or inhaled, and can cause irritation of the eyes or skin, nose and throat irritation, and excessive exposure may cause “dizziness, loss of balance and coordination, unconsciousness, coma and respiratory failure”. Repeated overexposure (assuming it doesn’t just kill you) can cause “central nervous system depression and liver and kidney damage”. The MSDS for Testors Model Cement provides details.
I’ve built plenty of models over the years without any obvious ill effect, and it’s not as bad as the Lexan glue below as they only recommend a respirator for exposure which “may exceed occupational limits”. In other words, use good ventilation and keep it off your hands, and you’ll likely avoid problems. Still, CA is a better choice (see above) if you can work with the quick setting time and other limitations. A respirator with an organic vapor cartridge is effective against toluene, so if you really want to be less exposed, wear one.
PVC Glue
PVC is normally glued using a solvent containing MEK, acetone and other compounds. This has all of the issues of MEK and acetone (see above), with additional concerns due to other chemicals typically included.
The MSDS for one brand notes that the fumes are considered carcinogenic in California.
Lexan (Polycarbonate) Glue
Polycarbonate (often known by its brand name, Lexan), can be glued using super-glue, but a strong bond requires use of a Methylene Chloride (also known as Dichloromethane) solvent glue to weld it. This stuff is very nasty; the MSDS recommends storage in an outdoor facility, forced-air respirators and disposing of clothing after use, although those cautions likely apply mainly to industrial use. It can be breathed in or absorbed through skin. One of its side effects when inhaled is production of carbon monoxide in the blood, which can lead to respiratory failure and death. It also eats rubber, so gloves have a limited lifespan. And it attacks plastics, so it probably can’t be used to attach styrene to Lexan anyway.
Dichloromethane used to be used in paint strippers and similar substances. Per wikipedia, in 2010 OSHA/NIOSH warned that 14 people using it for bathtub refinishing had died since 2000.
All things considered, this isn’t a substance I want to be working with.
If you are going to work with it, a respirator with a fresh organic vapor cartridge, coupled with good ventilation, is recommended. Note that the level of exposure at which it is absorbed (not necessarily harmful, until/unless you absorb enough) is below the level at which you can smell it, so the “replace respirator cartridge when you smell something” guidance isn’t going to help here.
3M Super 77 and Hi-Strength 90 Aerosol Glues
There are two 3M aerosol glues of potential interest: Super 77 and Hi-Strength 90. The former is a general-purpose adhesive available in most craft stores, and the latter is a specialty glue found in home supply outlets. The two are applicable to different situations. There is a useful table showing which are appropriate for bonding various combinations of materials on this site. There is a large degree of overlap, and both work with paper, plastic (styrene and acrylic) and wood, but Hi-Strength 90 in particular is useful for joining metal to various substances, including metal and plastic.
Both are flammable and should not be used around open flame or other potential ignition sources. Both can cause mild to moderate skin and eye irritation, and “central nervous system depression: symptoms include “headache, dizziness, drowsiness, incoordination, nausea, slowed reaction time, slurred speech, giddiness, and unconsciousness”. And both, in a single above-recommended exposure, can cause an “irregular heartbeat, faintness, chest pain, and may be fatal”. Both also “contain a chemical or chemicals which can cause birth defects or other reproductive harm”.
While the Hi-strength 90 is more toxic (and has a longer list of dangerous ingredients with more cautions), the Super 77 MSDS contains an additional warning that prolonged or repeated exposure (not overexposure, but exposure) can cause “Peripheral Neuropathy: Signs/symptoms may include tingling or numbness of the extremities, incoordination, weakness of the hands and feet, tremors and muscle atrophy.”
Both recommend use with “adequate” ventilation and a respirator (generally a good idea when working with any aerosol paint or glue, but this one recommends organic vapor cartridges, so it’s not just the particulate glue that’s of concern but the gasses as well), gloves, and safety glasses with side shields.
I used Super 77 for my initial backdrop glue, before discovering Paper Mod Podge, and used it outdoors, wearing a respirator with fresh “organic vapor” cartridges. After all that, it didn’t do a great job of attaching photo paper to a hardboard backdrop, and the photos peeled after a year. I switched to Paper Mod Podge, which doesn’t require all those precautions and has lasted more than six years so far without issues. This is one of those cases where the safer chemical was also the preferable one.
Other Chemicals
This section contains other chemicals used on or around a layout that do not fit in other categories.
Acetone
Acetone isn’t specifically a glue, but is a compound used with glues. Common uses include as a thinner or removal agent for cyanoacrylate glues (super-glue) and as a primer for and component of PVC glues. It is also used as a nail-polish thinner or remover, so you might think it relatively harmless. You’d be wrong.
Acetone is a skin irritant, and can permanently damage eyes, it’s also obviously a problem if swallowed or inhaled. Acetone is a central nervous system toxin and repeated exposure can potentially damage internal organs. It’s also considered a “developmental toxin”, so use by children and pregnant women should be avoided. And it is highly flammable, so avoid smoking or using open flames or anything creating sparks (like a model train motor) near it. Infrequent exposure to small quantities may not be a serious problem.
Use safety glasses and work in a well-ventilated area, and wash hands promptly with soapy water if exposed. A vapor respirator and gloves are recommended by the MSDS.
Nitrile gloves provide some protection, but are not as good as neoprene, and even latex may be better (one of the few things for which this is true).
As noted, acetone is used in nail polish, but the consensus there seems to be that the small amounts used do not pose a problem unless you are both pregnant and have an occupational exposure (i.e. are a salon technician), and even then it’s something of a gray area. So hobby exposure is probably not a significant risk even if pregnant, but gloves are a simple precaution.
Isopropyl Alcohol
Isopropyl alcohol, typically in a 50% or 70% solution with water is used as a cleaning agent for track. At higher concentrations it will strip paint from plastic models, so weak solutions are preferable except for stubborn grease.
Isopropyl alcohol is both flammable and toxic, but fairly safe relative to other chemicals. It can be used externally in small quantities for sterilization or as rubbing alcohol, so gloves are not required, but may be advisable when making extensive use of it. It should be kept away from open flame, and the vapor is heavier than air and could migrate to typical basement ignition sources such as furnace burners if used in large quantities without some form of active ventilation.
