bencav84

Good evening. Just an odd question. I have noticed a few people refering to rubbing alcohol. What type of alcohol is this? I am thinking Methylated Spirit (Denatured alcohol)?? Please tell me as thats what I need to thin epoxy to paint ye olde firewalls this weekend!!

Thanks!

Ben

carlosponti

My Feedback: (1)

rubbing alcohol is isopropyl alcohol. Im not sure if you could use Denatured Alcohol for thinning epoxy but i am guessing no. I have used Isoproyl acouple of times to thin epoxy.

iron eagel

rubbing alcohol is a term for either isopropyl alcohol (isopropanol) or ethyl alcohol (ethanol) rubbing-alcohol products. The confusion comes from the greater popularity of isopropyl rubbing alcohol, and as a result, individuals requesting "rubbing alcohol" generally expect and get an isopropyl alcohol product. However, the British Pharmacopoeia and United States Pharmacopeia standards (standards recognized in many countries other than just the UK and USA) define rubbing alcohol as a mixture of ethanol and water of fixed proportions.

Alcohol with water should only be used for clean up, not thinning of epoxy, it will weaken the epoxy. You are better off using either MEK or acetone to thin epoxy if you have to.

JohnW

My Feedback: (6)

The prefered solvent for thinning epoxy is MEK or Acetone. Methanol/ethanol works too. Rubbing would work, but would be my last choice due to the high water content. My first choice would be to use a low viscosity laminating epoxy such that I didn't need to thin the epoxy in the first place.

heh, iron posted while I was typing... ditto.

carrellh

In the pharmacies local to me you can get a few different versions of 'rubbing' alcohol. They all seem to be mixtures of isopropyl alcohol and water; with some having additional ingredients.
We have 70% alcohol with 30% water, and 91% alcohol with 9% water. These are clear liquids.
Sometimes I see green liquids that have menthol, and possibly other ingredients, added.

I use the 91% isopropyl for cleanup, thinning epoxy, first aid, etc.

Methylated Spirit (Denatured alcohol) is a good epoxy thinner. It is usually 99% (or more) pure so it has little water in it. Locally it costs more than isopropyl.

carrellh

A good way to thin epoxy, especially for fuelproofing, is to use heat. Mix the epoxy and put a blob on the surface. Use a heat gun or hair dryer to warm it and it will get as runny as water. Use 30 minute epoxy for this. The epoxy will cure quicker than normal when it's heated, so you do not want to use the 6 minute kind.

MinnFlyer

My Feedback: (4)

While MEK, Acetone and Denatured Alcohol are the best choices for thinning epoxy, if you're thinning it for fuel-proofing purposes there's nothing wrong with using rubbing alcohol.

Yes, it has water in it, but you're laying it on so thin that most of the water will evaporate.

And true, not all of the water will evaporate, leaving the epoxy weaker, but you don't need strength for fuel-proofing.

I have been doing it this way for over 20 years with no problem. Althought nowadays, I use Acetone only because I now keep it in stock, but if I were out, I wouldn't hesitate to use rubbing alcohol.

<EDIT> To answer the original question, "Rubbing Alcohol" is what a doctor would rub on your arm before giving you an injection.

bencav84

Cheers,

I love the quote about the pharmacopoeia(s) I work as a Analytical Chemist so they are my bible!! I looked in there but couldnt imagine using watered down isopropyl to thin glue down (what the brits call 70% IMS - industrial methylated spirit) There is too much jargon in those books to make any sense of, then add the french and Japanese versions into the mix and its just extracting the urine!!

I have access to all of these mentioned above, so form what I gather, for thinning epoxy : Acetone is top dog
How about cleaning up epoxy after making a join? Would acetone remove colour from the film or casue other damage? Would real rubbing alcohol be better on this case?

Thanks for your thorough and quick responses.

Ben

carlosponti

My Feedback: (1)

pretty much all i have ever thinned epoxy for was for fuel proofing. good to know

MinnFlyer

My Feedback: (4)

Acetone won't hurt most coverings. I can't speak for all of them, but it won't hurt MonoKote or Ultracote. But I use alcohol for clean up (Denatured OR rubbing) just to keep the odors down.

foodstick

I admit i have thinned epoxy with rubbing alcohol for years with no bad effects.


One thing that I might recommend for Gasoline guys, as I haven't experimented with this product and glow fuel .

P.O.R. its a Paint Over Rust product for auto restorers. I love the stuff I use it for firewalls and anywhere else wooden that I want sealed, its fairly expensive..maybe 15 bucks a pint...but it goes a long ways, it seems like epoxy once dried. I usually double coat. One warning, once the can is open the timer starts..might only go 6 months at most.. the stuff is so tough that if you don't put plastic between the lid and the can you will be CUTTING it open next time. Also, you get it on your skin and it dries..it will be there for a week, minimum..

Gray Beard

My Feedback: (-1)

I haven't had any color problems with Acetone on the plastic covering either. When I strip the covering off of A plane and there is coloring left over on the wood from the glue/pigment I use acetone to remove it so it doesn't darken the new covering. For thinning epoxy for fuel proofing I use the 91% alcohol, I stock both Acetone and Alcohol in my shop. I also have finishing epoxy and A heat gun, just depends on what I'm doing. Don't limit yourself, try different things until you find what you like.

bencav84

Indeed, The chassis cross member of my '78 MG roadter is painted with POR - spill it at your peril, it will NEVER come off. Not used it on a plane though!!

Thanks again for your hel;p, I can now clean and fuel proof happily and safely!!

Ben

bkdavy

My Feedback: (1)

I used to thin 30 minute eposy about 50 percent with Acetone. Acetone is made for the purpose of thinning epoxy (read the label on the can) and its not expensive (about $14 for a 1 quart can that has so far lasted about 4 years).

I quit thinning epoxy when I finally tried finishing resin. Its primarily used for fiberglassing, but more importantly its already thin enough to use for a quality fuel poofing job.

Try it, you'll like it.

Brad

fokker20planes

Denatured alcohol is primarily ethyl alcohol (The stuff you drink) and has either Isopropyl alcohol or Methyl alcohol added to make it poisonous so you wont drink it. Where I work, the Denatured alcohol is 92% ethanol, 4% isopropyl alcohol and 4% Methyl alcohol. I don't want to preach, but all of these are very flammable and require a lot of ventilation when using. Although none appear to be carcinogens all are really harmful if misused.

jetmech05

I would never use MEK around the house...that stuff is pretty wicked.....bad for you, and very explosive....
I knew a guy that was using MEK to clean something in his kitchen, and burned his house down.....
MEK is absorbed into the body through contact with skin

JohnW

My Feedback: (6)

Sorry to hear about the house, but what was he cleaning? His stove... while it was on?

MEK really isn't any more dangerous than any other flammable solvent. Gasoline has a much lower flash point, and many of us keep that around the house for yard tools.

MEK it will enter the blood stream thru the skin, so I suggest not taking a bath in it, but it is pretty hard to get a dangerous level of MEK in you without feeling like crap first, so dangerous overexposure is pretty difficult to pull off unless you really try.

MEK is superior to other solvents in a lot of respects. I love the stuff and always keep some around. But like anything, read the label warnings before use.

Sport_Pilot

Denatured alcohol is not only good for thinning epoxy but better than rubbing alcohol. Mostly because rubbing alcohol has a large percentage of water. The water will cause the epoxy to be weaker than it otherwise would be because most of the water will not evaporate before it sets.

da Rock

Yes, you can use Denatured Alcohol to thin epoxy, but WHY do it?

Why, because it's better than the alcohol sold in US drug stores that has a HUGE percentage of water in it.

Drug store, Isoproply, and Denatured will all thin epoxy. But the drug store is a bad choice. The Isoproply you find around (usually in drug stores and with water in it) is equally bad. Denatured is ok since it has no water and won't absorb any appreciable amount before it's used up if you handle it sensibly. But why bother with any of those.

Acetone is made to thin epoxy.
It is easily available. There are hardware stores and home improvement stores all over the place. And a can of it is almost as cheap as the Denatured that's in the same store. And they're both cheap.
Acetone also cleans dried CA off of Ultracote and Monokote. And cleans them in preparation for patching.

Why use something that degrades when you can use something that doesn't? And costs about the same.

MinnFlyer

My Feedback: (4)

There is a very simple and very logical reason for using Isopropyl Alcohol...

While many of us have a nice work shop and/or garage full of tools and gadgets, many modelers don't. For many years all I had was an apartment and kitchen table. What with being young and raising a family, I didn't HAVE an extra 4 bucks to spend on a can of Acetone, nor did I have a safe place to keep it.

But there was always a bottle of Isopropyl Alcohol in the medicine cabinet

Another logical reason for using it: It's late at night, tomorrow you're planning to get a lot of work done, but you need to fuel-proof something first. You're all out of other solvents and don't want to crank up the heat gun for fear of waking "She who must be obeyed". BUT, there's a bottle of Isopropyl Alcohol in the medicine cabinet!

I wouldn't think twice about using it, OR worrying about the water content. I don't need strength, I need fuel proofing and I need it NOW!

iron eagel

I agree totally with what you are saying here.
But I never use epoxy for fuel proofing, there are far lighter materials for this.
I only use epoxy when I am looking to add structural strength, glassing or as an adhesive when other things will not work, because of its weight.
And I know about not having a workshop, and using the kitchen table or piece of plywood in my lap.
I am luck enough that I have a workshop today and do not get yelled at for messing up the table.

foodstick

I think some of us just build so strong we need a weaker fuel proofer...just to even it out with the other guys !! ha ha ha ha Nah, I fall into the its right there on the shelf handy group. though I mainly use por anymore...

bencav84

Ok, I will use acetone, cant get it in shops in the UK (at least not normal DIY stores) but being a chemist, I have access to all types of things (and know all bout hazards etc...)

Out of interest, is MEK an abreviation or a trade name? I dont recall seeing nor hearing of it before!

Thanks!!

Ben

JohnW

My Feedback: (6)

Abreviation, not trade name. MEK is methyl ethyl ketone.

MinnFlyer

My Feedback: (4)

Methyl Ethyl Ketone