HELP! Thinners are making my head hurt! (Not literally)

[Robert Porter]

I am sure this topic has been covered in pieces, but am hoping someone can help me understand the big picture. I am having a tough time knowing what to use to thin what.

Enamel Paints I use enamel thinner (Paint Thinner?)

Acrylics I use either the branded one for that brand or lately I have been using a homebrew mix of Windex, Water and a few drops of glycerin which works well.

Not sure when we get to polyurathane based acrylics etc.

I decanted a spray can of Tamiya Grey Surface Primer and the only thing that works to clean my airbrush after spraying that is Enamel Thinner. Mineral Spirits don't touch it, and of course airbrush cleaner does not either.

So my questions are, what the heck is in the rattle cans of Tamiya Surface Primer?

And more important can someone concisely explain the differences and uses for the following? I have seen some used interchangeably. Especially lacquer thinner used with enamel paints for example.

I know this is asking a lot, but it is also a question that seems to be asked in different ways over and over by many folks. Maybe my ignorance can be the start of a summary answer?

1. Lacquer Thinner
2. Enamel Thinner
3. Mineral Spirits
4. Acetone
5. And the dozen or so other cleaners/solvents in the hardware store.

One thing of note, more and more paints are not true anything, but blends, for example MRP paints say they are an lacquer based acrylic. And we have polyurethane acrylics etc. So for non chemists like me it is getting more and more confusing.

 

[Crimea_River]

I can not give you a thorough answer to this wide topic but will offer the following:

- Tamiya's grey primer, at least the one in the bottle, is lacquer based so you will want to use lacquer thinner
- I exclusively use Tamiya's proprietary thinners for their acrylics. I have heard that the yellow-capped bottle is better for spraying than the white capped one but have really not found much difference.
- lacquer thinner is pretty "hot" (i.e. very reactive) so is great for cleaning dried paint off of anything, but will also eat your plastic. It's fine for thinning the appropriate paint though.
- I would suggest that you consult the manufacturer's recommendations in regard to thinners, though most will try to bum their products on you. There are several thinners for enamels and I've had varying success back in the day when I used them. Lacquer thinner should work in small quantities but I have found that adding lacquer thinner to a bottle of enamel in storage tends to make the stuff congeal over time so it's probably not the ideal product for that.
- The best thinners for acrylics vary by the product. Some work for some but not for others. so I think there's a danger in making general "one size fits all" recommendations.

 

[Airframes]

Can't help regarding acrylics (they're the work of the Devil !), but for true enamels, such as Humbrol, MM, Revell etc, then White Spirit, which is basically a Turpentine substitute, should do the job without problems.
It may be known under a different title in the USA, but it's the stuff you'd get at a large hardware outlet, for thinning oil-based household decorating paints and cleaning brushes, and is clear, like water (or vodka !).
I normally buy a 2 liter container, for around £4.

 

[Robert Porter]

So I went to my local hardware store and they have the following.

Paint Thinner (Bottle says for Oil Based Paints and Enamels)
Lacquer Thinner (Bottle says for Oil Based Paints and Varnishes)
Mineral Spirits (Does not work on whatever is in the Tamiya Spray Can but says it works for Oil based paints.)
Acetone (Bottle says remove project residue, helpful that)
M.E.K. (Huge Skull and Crossbones on this one, says Oil Based paints and varnishes)
Pure Gum Spirits Turpentine (General purpose cleaner)
Xylene (Which on the bottle says thins enamels and epoxy's)
VM&P Naptha (I don't think this is a thinner its a covering.)

As I mentioned the Mineral Spirits which I have, don't put a dent in the spray can stuff from Tamiya. Nor does Tamiya's own thinner X-20 which is meant for their acrylics.

5 of the above all say Oil based products, but only one, the regular old Paint Thinner works on the Tamiya stuff. Smells just like the clear stuff Testors sells as Enamel Thinner which also works on the Tamiya Spray can stuff which in turn leads me to believe the spray can stuff must be enamel based.

If I remember correctly Xylene will work on pretty much anything but also eat the seals on my airbrush.

 

[Robert Porter]

I can not give you a thorough answer to this wide topic but will offer the following:

- Tamiya's grey primer, at least the one in the bottle, is lacquer based so you will want to use lacquer thinner
- I exclusively use Tamiya's proprietary thinners for their acrylics. I have heard that the yellow-capped bottle is better for spraying than the white capped one but have really not found much difference.
- lacquer thinner is pretty "hot" (i.e. very reactive) so is great for cleaning dried paint off of anything, but will also eat your plastic. It's fine for thinning the appropriate paint though.
- I would suggest that you consult the manufacturer's recommendations in regard to thinners, though most will try to bum their products on you. There are several thinners for enamels and I've had varying success back in the day when I used them. Lacquer thinner should work in small quantities but I have found that adding lacquer thinner to a bottle of enamel in storage tends to make the stuff congeal over time so it's probably not the ideal product for that.
- The best thinners for acrylics vary by the product. Some work for some but not for others. so I think there's a danger in making general "one size fits all" recommendations.

Your comments on lacquer thinner match my experience. I have heard it mentioned as being used with enamels to prevent tip dry and act as a flow improver etc. Thanks!

 

[Robert Porter]

I can not give you a thorough answer to this wide topic but will offer the following:

- Tamiya's grey primer, at least the one in the bottle, is lacquer based so you will want to use lacquer thinner
- I exclusively use Tamiya's proprietary thinners for their acrylics. I have heard that the yellow-capped bottle is better for spraying than the white capped one but have really not found much difference.
- lacquer thinner is pretty "hot" (i.e. very reactive) so is great for cleaning dried paint off of anything, but will also eat your plastic. It's fine for thinning the appropriate paint though.
- I would suggest that you consult the manufacturer's recommendations in regard to thinners, though most will try to bum their products on you. There are several thinners for enamels and I've had varying success back in the day when I used them. Lacquer thinner should work in small quantities but I have found that adding lacquer thinner to a bottle of enamel in storage tends to make the stuff congeal over time so it's probably not the ideal product for that.
- The best thinners for acrylics vary by the product. Some work for some but not for others. so I think there's a danger in making general "one size fits all" recommendations.

My homebrew thinner seems to work fine for Model Master Acrylics, Vallejo Acrylics, and Tamiya Acrylics. But it does not work well with Metallic Acrylics or several other brands, so I agree there is no one size fits all approach. It is more confusing than I would like to know what to use when. For instance I use acetone in combination with several puttys to smooth them. But even there it only works on some.

 

[Airframes]

I don't use the stuff, but as the Tamiya product is a primer for acrylics, then it will be either an enamel, or polyurethane enamel based product.
If the Paint Thinner works, then it's probably the equivalent of the White Spirit mentioned earlier, and suggests that the Tamiya primer is enamel.

 

[Crimea_River]

Stay away from MEK. It's nasty sh!t.

https://www.sciencelab.com/msds.php?msdsId=9927358

 

[Robert Porter]

I don't use the stuff, but as the Tamiya product is a primer for acrylics, then it will be either an enamel, or polyurethane enamel based product.
If the Paint Thinner works, then it's probably the equivalent of the White Spirit mentioned earlier, and suggests that the Tamiya primer is enamel.

Thats the conclusion I came to as well. Sheesh, you end up having to have an arsenal of different thinners just to handle two main types of paints.

 

[Airframes]

Yep, MEK is used in various industries, often as a cleaner for metal surfaces, such as litho printing plates,and some of the 'specialised' modelling adhesives of the 'weld' type are basically MEK.
Too much on a plastic part will dissolve it, and the fumes are dangerous - oh, and it can also be used as a contact explosive, but I won't tell you how !

 

[Robert Porter]

Yep, MEK is used in various industries, often as a cleaner for metal surfaces, such as litho printing plates,and some of the 'specialised' modelling adhesives of the 'weld' type are basically MEK.
Too much on a plastic part will dissolve it, and the fumes are dangerous - oh, and it can also be used as a contact explosive, but I won't tell you how !

Aww now thats no fun! I have visions of creating exploding tennis balls dancing through my head now!

 

[Airframes]

Well, what you do is ................... Oh, hello Officer, I was just ........................................

 

[Robert Porter]

Well, what you do is ................... Oh, hello Officer, I was just ........................................

Ah yep! And googling for stuff like that can lead to a visit from our lovely federal gestapo, I mean FBI!

 

[Brett G]

Is it permissible to post links to YouTube videos here? A person in a Google+ group I am a part of did a very good video of the different thinners and their specific uses, as well as workable crossovers. He used a very scientific approach (he's an engineer, or something), and really answers most of the common questions to a degree even knuckleheads like myself can understand.

 

[Robert Porter]

Is it permissible to post links to YouTube videos here? A person in a Google+ group I am a part of did a very good video of the different thinners and their specific uses, as well as workable crossovers. He used a very scientific approach (he's an engineer, or something), and really answers most of the common questions to a degree even knuckleheads like myself can understand.

Yes it is, or at least I believe so. The biggest prohibition is if the video or post is trying to sell something.

 

[Night Fighter Nut]

Fine Scale Modeler had an article about thinners and paints some time back and I believe I have a copy of it as well as an extensive subject book on airbrushing. I have heard of people cutting the acrylic paint with either Windex or alcohol. Let me check my materials and see what I come up with.

 

[Robert Porter]

Fine Scale Modeler had an article about thinners and paints some time back and I believe I have a copy of it as well as an extensive subject book on airbrushing. I have heard of people cutting the acrylic paint with either Windex or alcohol. Let me check my materials and see what I come up with.

Thanks, my plan is to put together as comprehensive of a list as I can and publish it here. So I will collect all the info any of you are willing to share happily!

 

[mikewint]

Seems like we had a thread sometime back on this. The confusion results from a number of factors exacerbated by modern chemistry and no universal control of terminology
Enamel paint is a term that is used to reference a paint with a hard, glossy and opaque finish. In actuality, the term "enamel paint" does not necessarily have a generally accepted or standardized definition, but historically, enamel paint has been used to refer to any type of enamel paint that is oil based and with a considerably glossy finish. They are available in several types, including oil based or alkyd based, which have the features of slower drying times in addition to being harder than that of water based enamel paints. Oil based paints are recognized by their distinguishable solvent odor properties and are easily cleaned using paint thinner or mineral spirits. Additionally, quite a few manufacturers now add varnish to oil based paints.
Drying oils are a key component of oil paint and some varnishes A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air. The oil hardens through a chemical reaction in which the components crosslink by the action of oxygen (not through the evaporation of water or other solvents).. Some commonly used drying oils include linseed oil, tung oil, poppy seed oil, perilla oil, and walnut oil. Their use has declined over the past several decades, as they have been replaced by alkyd resins and other binders. These drying alkyds are also cured in air. The drying speed and the nature of the coatings depends on the amount and type of drying oil employed (more polyunsaturated oil means faster reaction in air) and use of metal salts, the so-called oil drying agents. These metal complexes catylyze the crosslinking of the unsaturated sites.
The drying time will vary in accordance with the type of enamel paint being used, the drying conditions and environmental conditions. Oil based enamels fully dry in 8 – 24 hours and dry on the inside first and then outwards. It is easy to tell when an oil based enamel has fully cured, as it will feel entirely dry when touched. For this reason, second coats are applied while the original coat is "tacky". This assures that the second coat adheres to the first coat and so on.
On the other hand, water based enamels can take up to one full month to set and can be damaged during that time, so a high degree of care should be exercised when washing and handling. Water based enamel paints will dry on the outside first and then the inside. An outer covering will form on the surface and although the paint will feel dry to the touch in approximately one hour after application, the underlying paint will still be moist. Weather plays a hand in the drying time of the paint. When there is a high degree of humidity or it is on the cool side, the enamel may take up to several weeks to cure completely.

Mineral spirits/paint thinner are mixtures of aliphatic and alicyclic C7 to C12 hydrocarbons. For cleaning brushes, paint thinner is best since it's half the cost of mineral spirits and basically works the same. Other than the price, the differences between the two solvents are subtle: Both are petroleum products. Both can be used to thin oil-based paints and varnishes and to clean paintbrushes. Paint thinner is mineral spirits, but in a less refined form. It contains other types of solvents, which makes it a lot smellier and more volatile. Mineral spirits are not as stinky. Because it's more refined, it's slightly more effective in smaller quantities than paint thinner.

Turpentine is a fluid obtained by the distillation of resin obtained from live trees, mainly pines. Turpentine is composed of terpenes. The word turpentine derives from the name of a species of tree, the terebinth tree. Mineral turpentine or other petroleum distillates are used to replace turpentine, but they are very different chemically.

Acrylic paints have an acrylic resin binder and use water and/or alcohol as a liquid. They are easy and safe to use, permanent, quick drying, low odor and are suitable for brush and airbrush.
Drying time for acrylic paints is affected by many factors – how heavily it is applied, temperature, humidity, mediums used, brand, and color, to name a few – but most acrylic paints will be touch dry in 20-30 minutes. This does not mean they are cured. Cure time is when the acrylic film is fully stable, close to its maximum durability, water resistant and less vulnerable to attack by mild solvents. This usually takes at least three days for thin applications and may take much longer (up to two weeks or more) for thick applications.
Since acrylics can be thinned and equipment cleaned with alcohol or water they are very user friendly. However, care is needed because they can dry very quickly and when dried are difficult to remove. Most manufacturers produce thinners for use with their own ranges and to be absolutely safe you should stick with these. Water and alcohol will act as a thinner with most paint ranges, but will not always give such good results and it is not always possible to mix acrylic paints from different manufacturers.

Lacquers (cellulose) care is needed with this term as it is often used to describe any sort of glossy protective coating, for example furniture is often described as having a lacquered finish. Sometimes a paint may be described as a lacquer when in fact it is an acrylic or enamel based gloss varnish.
A lacquer is distinguished from other paints by the solvent used which is cellulose. This makes it very different from other types of paint. Lacquer-type paints tend to be highly toxic and very strong smelling, fast drying, very flammable, and form a hard, durable, shiny finish (although some flat lacquers are available).
Because lacquers are very fast drying, highly toxic, flammable and very unforgiving they can be a real pain to use. However, they are popular with some modelers. The shiny hard wearing coat is ideal for auto models – particularly radio control which need to survive the real world. Lacquers are also great for realistic metallic finishes and one of the most popular ranges of metallic lacquers is made by Alclad.
Another range of lacquer paints popular with modelers is the 'Mr Color' range from Gunze Sangyo (not to be confused with their "Mr. Hobby" paint range). Tamiya produces a range of lacquer spray cans and Testors produce some clear lacquer coats under their Model Master range.
There is a weird contradiction with lacquer paints and plastic modeling. Cellulose melts plastic, so you might think that you would not want to get a lacquer paint in direct contact with the plastic surface. However, there are some lacquer based spray primers. Because the lacquer spray is so thin, it dries within seconds before it does any damage to the plastic surface, but it just has enough time to key into the plastic giving it very good grip.
Lacquers need to be applied very thin by spray can or airbrush in a very well ventilated area and with a protective mask. Alcohol, water and acrylic thinners will have no effect on lacquer paints. If anyone knows of a way to remove dried lacquer paint please let me know.
Due to their flammability many mail order and Internet shops will not ship them airmail so you might have to find a local source.
Personally, I would only use lacquer paints as a last resort, since I want to enjoy my hobby and they are just too unpleasant to work with. However, some modelers swear by them.

I never bought into the rule that says you can't apply a lacquer over any other type of paint. There are too many exceptions for this "rule" to be useful. There are many formulas for paints and the groupings are confusing. Lacquer and enamel paint have never been precise terms--they are not named from their ingredients. There is no universal governing body that sets out precise definitions for these types of paints. As a result, we get confused. The lines have become very blurred in the modern world. For example one myth is that all acrylic paints are water-based. There is no rule or law that says paints labeled acrylic must be water-based. Most acrylic paints are water-based, but that's because many acrylic polymers are water soluble. But acrylic polymers can also be soluble in alcohols, esters, and such. The term "acrylic" refers to the paint's solid film-former (binder). In chemistry terms, an acrylic polymer is based on the structure of acrylic acid. Thus if a paint's solid film-former is an acrylic polymer, then by definition it is an acrylic paint, regardless of which solvent(s) is used.
Tamiya's acrylic paints are not your typical acrylic paints. Tamiya uses alcohols and a glycol ether in addition to water as a solvent. But they as still acrylic paints. While Tamiya's acrylics probably are not lacquers, there is no rule that says a lacquer paint cannot have an acrylic binder (hence the acrylic lacquers in the auto industry).
I was taught that the general rule of thumb was that the "hotter" paints should not be applied over "cooler" paints.
In general terms, in order of "heat",
1. lacquer
2. enamel
3. acrylic
That is to say that enamels and acrylics can be applied over lacquers and acrylics over enamels safely.
However, we know that for many years, modelers have applied lacquers in the form of Testors glosscote/dullcote and Tamiya spray clear gloss/flat over enamels and acrylics with no ill effects.
Paint incompatibility happens when the solvents in one paint dissolve the binder in the paint underneath it. Since paint companies keep the binder ingredients secret, it is not possible to predict which solvents will dissolve which paints. Hence the cardinal advice is to always test on something other than your model, and always allow the paint to fully cure before applying another paint.

Lacquer thinner is the solvent and thinner used with all types of lacquer, including nitrocellulose, CAB-acrylic and catalyzed. It's the most interesting of the finish solvents because it's composed of half-a-dozen or so individual solvents. Solvents from all five of the solvent families are used in lacquer thinners. Toluene, xylene and "high-flash" (meaning fast evaporating) naphtha are from the petroleum-distillate family. The other four families are ketones, esters, glycol ethers and alcohols.
All the individual solvents from the ketone, ester and glycol ether families dissolve lacquer on their own and are called "active" solvents. But they evaporate at different rates, so manufacturers choose among them to make a thinner that evaporates in steps at the speeds they want.
Alcohol doesn't dissolve lacquer on its own, but it does in combination with these other solvents, so it is called a "latent" solvent. One or more of the alcohols is usually added to the mix to reduce cost.
The nature of lacquers is that they can be fully dissolved (meaning the lacquer molecules are separated) and still be too thick to spray without getting severe orange peel. So to further "thin" the lacquer (and also lacquer thinner) without adding expensive dissolving solvents, manufacturers add up to 50% toluene, xylene or high-flash naphtha. These solvents are called "diluents" or "diluting" solvents.
Because the diluting solvents don't dissolve lacquer, they have to evaporate fast enough to be out of the lacquer before all the dissolving solvents have evaporated. Otherwise, the lacquer will come out of solution and appear as white, cotton-like, particles on the dried finish.

 

[Robert Porter]

Thank you very much mikewint you made a complicated subject very easy to understand. Honestly I had a lot of the false assumptions you mentioned so this was more than just helpful it was educational. I have no idea what you did for an occupation but you have a real talent in communication skills!

As mentioned above my plan is to distill what I learn here and elsewhere into a layman consumable written guide and distribute such guide for free. If it is okay with you I would love to quote or reword some of your reply, with attribution of course?

Thanks again for taking the time to reply in such a comprehensive manner, truly appreciated!

 

[Robert Porter]

Attached is my first draft of collecting information. Please have a look and let me know if you think it can or does have value?

Edit: New Draft as of Jan 19, 2017. I will continue to update this post rather than repost each new revision.