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Topic: using surgical spirit to clean connections before desoldeirng? (Read 6546 times) previous topic - next topic

larryd

No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

ChrisTenone

Quit bragging Larry ... ;)

Methanol, ethanol and isopropyl alcohol are the three most common and lightest alcohols. They contain 1, 2 and 3 carbon atoms respectively. They are all flammable, volatile and toxic. Ethanol is the least toxic, and isopropyl alcohol the least volatile. Methanol is the most toxic and the most corrosive. Isopropyl alcohol is the best to use for cleaning flux residue, but ethanol evaporates faster. Methanol can cause micro-pitting on iron (or below in the activity series) surfaces, so should not be used.
What, I need to say something else too?

larryd

I use Isopropyl alcohol to remove the residue, before the alcohol evaporates wash the PCB in distilled water, then use an air compressor to blow off the water.
Things like switches, relays etc. that can be damaged by water, are soldered after.
.
No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

Noobian

What a load of bollocks! :smiley-roll:

It turns out that "surgical spirit" is by definition, "methylated spirit" which is 10% methanol, so rubbing it on the skin (and possibly introducing it into cuts) is exactly its intended application.

Calling methanol "super toxic" is quite an exaggeration.  The body has limited capacity for tolerating it so the small amounts involved in the reasonable use of surgical spirit - on the skin - or as a cleaning agent, are not dangerous.

The only concern might be the oily residue - or perhaps this might even be an advantage.
Mother of sweet bejeezus :smiley-eek:

It turns out that the methylated spirit "aka denatured alcohol" by definition is nothing but ethanol with 10% methanol additive. So basically the Surgical spirit which you mentioned is Ethanol based, and NOT methanol based. But that's B.P's version of surgical spirit, others use IsoPro with no methanol, instead of denatured alcohol.

Here's what your wiki page says about Methanol.
Quote
Methanol has a high toxicity in humans. As little as 10 mL of pure methanol, ingested, is metabolized into formic acid, which can cause permanent blindness by destruction of the optic nerve. 30 mL is potentially fatal,[16] although the median lethal dose is typically 100 mL

Methanol (whether it enters the body by ingestion, inhalation, or absorption through the skin) can be fatal due to its CNS depressant properties
The amount of methanol in Surgical spirit is of a considerably small amount, that is after the methylated spirit has been diluted with 30% Water.
But opening a bottle of pure methanol in a non ventilated room is by no means "small amounts" or safe.

and does any of these signs look like an exaggeration to you?








If you are really worried wear protection:
No, you must wear real full body protection :D

raschemmel

This is the only place in the world where a simple question can start WWIII...
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Paul__B

It turns out that the methylated spirit "aka denatured alcohol" by definition is nothing but ethanol with 10% methanol additive. So basically the Surgical spirit which you mentioned is Ethanol based, and NOT methanol based.
And that is what I said.  No-one ever suggested there was a version of "Surgical spirit" based on methanol.  If nothing else, it would probably be more expensive.

But that's B.P's version of surgical spirit, others use IsoPro with no methanol, instead of denatured alcohol.
No problem.

The amount of methanol in Surgical spirit is of a considerably small amount, that is after the methylated spirit has been diluted with 30% Water.
It is as stated, about 10%.  Dilution with water, if performed (rather unclear from these sources), would arguably reduce this to 7%.  Whether you consider this "a considerably small amount" is clearly relative.

Boardburner2

Surgical spirit traditionally was ethanol +water.
It has been largely superseded by isopropyl alcohol.

Methanol additives are only used for methylated spirit.
Industrial if you can get it is better than the store stuff as it can be had without water and the various chemicals added to prevent consumption.

All are acceptable cleaning agents but be aware that rubbing alcohols can contain lanolin or similar.
That stuff must be avoided.

EDIT

I prefer industrial meths as it leaves no residue and in smaller quantities is half the price of ispropyl.

gpsmikey

I use Isopropyl alcohol to remove the residue, before the alcohol evaporates wash the PCB in distilled water, then use an air compressor to blow off the water.
Things like switches, relays etc. that can be damaged by water, are soldered after.
.
I usually use a cotton swab with Isopropyl Alcohol to clean up after soldering etc. with rosin core solder (or before soldering to make sure I get any grease/oil etc.).  Be careful with the air compressor - many of them will have some oil in the air and end up contaminating the work area with oily air (that is why you can buy all those oil/water separators).  A diaphram type compressor is usually pretty clean, but if yours is like mine (2hp piston type), there is some oil in the air (blow it on your hand for a bit then rub your hands and notice the slight oil film).  Another issue with high pressure air if you are not careful - things like O-rings seal by pressure on them and while they can withstand quite a bit of pressure, fast moving air etc. does not give them a chance to seal and will sneak under to get inside (used to have that problem with diving watches where they were good to 200+ feet, but would flood in the shower where high speed water drops hit the seal and went under it.  They changed the design of the buttons so it can't do that, but it used to be an issue.
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3

Boardburner2

As an aside , i have used methanol in my helicopter for many years.
Never seen anyone at my club with protective gear on and no one has gone blind yet.

Noobian


Boardburner2

 :)
I just knew.....

The main risks are fire and prolonged exposure as with any hydrocarbon.
The odd splash should not be an issue.

If you are silly enough to drink it that very effectivley removes yourself from the gene pool.
Certainly wont be able to fly a model if blind.

Sensible precautions, do not use indoors, empty fuel tank before putting in car or workshop.

"median lethal dose is typically 100 mL"

I cant help but wonder how they arrived at that figure.

The double blind test takes on a whole new meaning.

raschemmel

Quote
I cant help but wonder how they arrived at that figure.
Autopsy report ?
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Noobian

Autopsy report ?
Naah!  Frankenstein "trial and error" :smiley-lol:





raschemmel

Quote
Naah!  Frankenstein "trial and error" 
I'm not sure if the Toxology Dept of a hospital is required to notify the FDA in fatal overdose cases but I doubt it. Even if they did they likely could not link it to a particular manufacturer but it could wind up in a database field under fatal overdose /methanol. The manufacturer may be required to request that information when they submit their application for product approval since the manufacturer's labeling department would need that to design their label. Their must be a national database for overdose data that the manufacturer can access using their license.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

ChrisTenone

I overheard a couple technicians in the stockroom, while drinking the wood alcohol. "Better hurry and drink up, it's getting dark."

What, I need to say something else too?

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