Cap Fur

[sr1200]

I was trying to work out a relay circuit for a project im working on and i inadvertently (not sure how) blew a cap. It was a tiny 10u 35v (smaller than a pencil eraser). Sounded like a fire cracker almost as loud as a .22.
I've NEVER had this happen before and i was met with an interesting sight. There was brown "fur" all over the circuit (along with a fun fly tape lookin coil). The brown fur is all over everything. What is it, how harmful is it and is it ok to just blow off, or should i hit it with some liquid cleaner of some sort?

 

[Rusan]

The electrolyte paste contains sulfuric acid, at least I know 'lytics did years ago. I'm not sure if it'll react with alcohol or not; I'd maybe try contact cleaner cleaner after blowing/wiping/scrubbing it off.

 

[sr1200]

Thanks. Im just worried its asbestos or something.

 

[Rusan]

I've never had a cap explode while breadboarding before; I bet that was an attention-grabbing experience!

I do know exactly what kind of pop 'lytics of all sizes make, however. About 30 years ago, a ham radio friend and I had a fun little apparatus that involved a DC to AC inverter, an old linear RF amplifier with the power and driver tubes removed, about a 150 foot spool of thick zip cord with alligator clips on one end and a tube base on the other, and whatever old electrolytic caps we had on hand at the time.

He had some land about 5 miles down a dirt road, and every now and then we'd go plink cans with our .22 rifles, and blow up caps when we had 'em. Connecting a 20,000uF/100V cap backward to 750V DC is some pretty tasty stuff.

 

[user 130681]

Not H2SO4.
Various liquid electrolytes are used in electrolytic capacitors today. Electrolytes containing ethylene glycol (EG) or boric acid are used mainly in medium to high-voltage electrolytic capacitors at temperatures of up to 85°C.
They have never used Sulphuric Acid.

 

[Rusan]

Not H2SO4. Various liquid electrolytes are used in electrolytic capacitors today......They have never used Sulphuric Acid.

I stand corrected. Probably 20 years ago, I'd read that the electrolyte contains sulfuric acid. I just now dug out that book and looked it up, and it wasn't aluminum electrolytics but the old wet slug tantalums that used sulfuric acid electrolyte. HATE those things...

 

[Monte McGuire]

The 'brown fur' is paper or cardboard, used to separate layers of the rolled up aluminum electrodes. Since the paper is soaked in electrolyte, it can cause corrosion if you don't remove and safely rinse away any / remove any spillage.

 

[JohnRoberts]

clean the fur off (alcohol?)...

I have seen small electrolytic caps fail explosively when hit with mains voltage...

I only had one film cap explode and that was back in the 60s working on an early DC to DC switcher (lots of high voltage spikes absorbed by that cap).

JR

 

[Tubetec]

While bringing a Hp200cd oscillator back to life , one of the ancient filter caps started ooozing out this funky black gunk ,luckliy no explosions though .

There was a buddy of mine years ago used put a led across the mains socket , then using a brush handle flick the switch , looking back now , not a smart thing to be doing at all .

 

[dmp]

Assuming it is a recently manufactured cap, it meets rohs (restriction of hazardous substances)

 

[JohnRoberts]

don't eat the cap fur....

JR

PS; Blowing up a metallized film cap made a dusting of little metal bits.

 

[sr1200]

don't eat the cap fur....

That actually made me laugh out loud when reading it! Thank you!
Yeah, i stupidly had a VERY loose connection to the 12v power supply which while i was trying to trace something out and it made/broke connection about 20 times in a split second (the relay went nuts) and BANG! the metal coil was kinda fun to poke at, was like fly paper curly.