Maybe this is a rather unusual question, bizare even, but for me it has turned into a bit of a dome-scratcher, as ol’ Col. Potter used to say. Articles on scenery building say to use isopropyl (rubbing) alcohol as a wetting agent. Articles on spray painting say to use denatured alcohol as a thinner for certain kinds of paint. My dictionaries (standard and medical) say that denatured alcohol is ethyl alcohol (“standard” alcohol) with something added to make it unfit to drink, which is the meaning of “denatured” and isoproply alcohol is too toxic for drinking–nothing special otherwise. My question is, given that they both appear to be similar if not the same, why can’t they be used interchangably for wetting agents and paint thinners?
Isopropanol and ethanol are not the same. They are different chemicals, CH3CHOHCH3 and C2H5OH respectively, with different properties.
During prohibition, ethyl alcohol was banned and companies who needed it eventually got denatured alcohol. The reason it’s still made is that it cannot be consumed and can made cheaply and get around taxation.
I use Isopropyl alcohol, but don’t do anything with denatured alcohol. I don’t know for sure, but I think that there is a difference between the two that make the incompatable for some projects, but am sure they could both dilute glue and paint.
Denatured alcohol is both a thinner and solvent for shellac, and any and all shellac based paints.
Seamonster, for making wet water, either isopropyl alcohol (isopropanol) or denatured ethyl alcohol would work - both will reduce the surface tension of the water they’re mixed with. However, as ericsp says, they are different chemically, and I would not mix them up as paint thinner - a paint that takes denatured alcohol as a thinner might react chemically with isopropyl alcohol. I have seen this happen, and the paint turned into latex goop. If you must use the “wrong” alcohol as a paint thinner, test it with a little bit of the paint first in a jar before loading up your spray gun.
Jim
I remember back in the metalic tape days, that you use denatured alcohol for cleaning the heads with a Q-tip. Isopropyl alcocol leaves a residue that degrades sound quality.
(So don’t paint your Broadway locomotives after thinning with isopropyl alcohol) [:o)]
Thanks for all the info, folks! Very enlightening. I guess I’ll have to change my thinking that alcohol is all the same. Ericsp, your formulas brought back some dim memories of high-school chemistry classes, long, long ago. Never did enjoy high-school chemistry and my only memories of it were almost setting the lab on fire and making stink bombs. I guess I’ll have to get some denatured alcohol for paint thinner, but I’ll stick with diluted white glue for scenery. It works very well for me and is easy to soften and remove. I tried the alcohol/water mix once–it didn’t work for me as well as diluted white glue and the smell of that much alcohol bothered me. Proper paint thinning can get a bit complicated, so I’m trying to stick to water-based paints, mostly for the sake of my 11 y.o. granddaughter who loves painting structures and people and putting down scenery and is very good at it.
Methanol is the secret ingredient added to denature ethyl alcohol (ethanol). If you consume it, it causes blindness.
Since we are on the subject, how is Isoproply made and why does it cause the residue?
Idle curiousity on my part. 
Isopropyl alcohol is usually diluted with water to to about 70%, but I don’t recall the process for making it.
Stumper
The residue actually comes from the water used to thin out the alcohol solution to 70% (the most common), and if they didn’t use distilled water, the minerals in the water are left behind when the alcohol/water mixture evaporates. Some of the residue could also be left over from the model-making process, which isn’t obvious until the alcohol wets it and then dries. Like the recommendation of cleaning before painting, you can help this by washing the model in a warm water & mild detergent solution before applying any alcohol washes.
Once way to minimize residue is to use 91% alcohol mixtures, which leave little or no residue due to the decreased water content. I usually use this one for ink washes. You can also sometimes find 99% alcohol mixes, but I find their smell to be too overwhelming, and at that concentration it’s also just about a pure desolving agent, and could strip some paints, adhesives or decals off the model.
I think that I saw a chemical company’s website that told a little about their manufacturering processes (of course that was in the late 1990s), if I remember correctly, one way to manufacture isopropanol (or was it acetone) is as a coproduct in the manufacture of phenol (of course I am trying to remember this from information I saw a few years ago). Here is a link that might be interesting.
http://www.dow.com/webapps/lit/litorder.asp?filepath=oxysolvents/pdfs/noreg/327-00031.pdf&pdf=true
Search for isopropyl.
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1…
To find more information get the patent numbers from (http://www.rohmhaas.com/ionexchange/IP/hydration_references.htm), then put the patent numbers (one at a time) in the query box at (http://patft.uspto.gov/netahtml/srchnum.htm).
I have also heard of using gasoline for the denaturant for ethanol that will be used as an oxygenate for gasoline.
Just recently I saw on a computer forum a question about cleaning LCD screens on laptop computers as well as desktop LCD screens.
The answer was to use Rubbing Alcohol as the screens were cleaned with that before they left the factory. However they didn’t say which to use…?
I have yet to try it, but since I have 3 of these screens, I’m sure sooner or later I will.
gtirr
I guess alcohol wouldn’t hurt a glass screen since professional window washers use it to keep the water in their buckets from freezing onto windows in cold weather, and I believe it’s also in winter grade automobile washer fluid. I use regular glass cleaner with ammonia to clean my computer screen and it does an excellent job. However, it’s a no-no if the glass is coated. I have coated eyeglass lenses and the optician warned me against using glass cleaner on them. Of course, they want to sell me their bottles of lens cleaners, but she admitted that distilled water was also quite good. BTW, glass cleaner with ammonia is an excellent cleaner for whiteboards and doesn’t have the overpowering odor of whiteboard cleaner. I discovered this by accident one day when I ran out of whiteboard cleaner, and never used it again.
Going back to SpaceMouse’s comment on rubbing alcohol for cleaning tape heads, if memory serves me correctly, that’s what was commonly recommended for that job, and I always used it on tape heads without any problems.
…Bob
Rubbing alcohol is isopropyl alcohol (isopropanol). As spacemouse notes, it tends to leave a residue behind.
Jim
Haven’t I been reading that blue windshield washer solution is a good paint thinner for airbrushing?
Hey spacemouse: You just gave your age away!!![(-D][(-D][(-D]
Was your alcohol kept next to the 8-track player?!?!?! Mine was.
Oooops! Just gave my age away!!![:0]
My company uses IPA as found in your local drugstore 70% mix. I blend it with 2 other trade secret chemicals and use it as part of a stripping solvent for leather. Straight IPA will degrease nicley. We used this to wash our gas powered RC cars years ago. ALSO it blows up very nicley when it is atomized by a sprayer. Guy in the shop! Smoking, IPA in spray bottle nad FULL BEARD, BOOM no BEARD. I am working on VERY VERY inexpensive water based scenery dye. Looks like about $10.00 per QUART will be the price. Still doing R&D but looks GOOD and is water based.
OK, short chemistry lesson.
Methanol has 1 carbon atoms, 3 hydrogen atoms, and an -OH (alcohol functionality).
Ethanol has 2 carbon atoms, 5 hydrogens, and an -OH attached to one of the carbons.
Iso-Propanol has 3 carbon atoms, 8 hydrogens, and an -OH attached to the second carbon in the chain. The -OH is “like” HOH, which is water, so it is extremely soluble in water. The carbons are “like” the solvents in paints, oils, and grease, and cause the alcohols to be soluable in them to varying degrees.
Methanol is used in windshield washer fluid to cut road film on the windshield and to prevent the washer fluid from freezing. Washer fluid is water with methanol added.
Ethanol is derived most often from the fermentation of biomass (starches and sugars) and is consumable. Since the government wants to tax everything that is enjoyable or sinful, you get to pay taxes on a “proof gallon”, which is actually twice an actual gallon. 80 proof alcohol is 40% by volume. Denaturing grain alcohol is a way to make this useful solvent unfit for consumption and to avoid having to pay taxes on it. Even so, it is strictly regulated and inspected by the government.
Isopropanol has a larger carbon chain and is different in that the alcohol functionality (-OH) is in the middle of the molecule instead of on the end. You remember the smell from doctors’ offices where it is used to sterilize instruments and your skin before you get poked. It is toxic to drink. It reacts differently than both methanol and ethanol to various organic compounds (paints, oils, adhesives, plastics).
I hope this isn’t too much information, but they are significantly different and therefore uniquely versatile.
Mark C.