Is this only true of electrolytics? I'm pretty sure that I'd want it right to get good ADC readings.
Electrolytic and tantalum (a type of electrolytic) capacitors are polarized. Ceramic, monolithic, and foil capacitors are not.
In the video, he's talking about foil capacitor which are not generally considered polarized. I'm a bit skeptical about what he's saying... There may be some rare circuits where the "polarity" (orientation) of a non-polarized capacitor might make a difference, but I've never heard of such a case...
There's a reason the manufacturer's datasheet doesn't specify a polarity and a reason why they are not polarity-marked.
If you are unsure, check the datasheet.
As a rough-general rule, capacitors less than 1uF tend to be non-polarized and caps 1uF or greater tend to be polarized.
There are higher-value foil capacitors and there are non-polarized electrolytics. The most common use of these is in speaker crossovers where you need fairly high-value non-polarized caps for the AC audio signal.
Most capacitors made to day do not have this shielded foil.
You may come across old stock.
This was more prevalent in high voltage high impedance vacuum tube circuits.
As suggested, this was for shielding not for capacitor polarity protection.
.
Well, in fact, although this does apply to electrolytics, he did not mention them and for a good reason - with electrolytics it is not negotiable as there is only ever one possible way of connecting them; it relates to DC polarity and not shielding; he was not talking about that at all.
That guy clearly has a couple of fetishes.
One is the use of obsolete vacuum FETs. The other - and related - well, just look at his workshop background, you could not possibly use more than two of those and he has dozens. And even more perverse - he can actually find things on his bench! I am however envious of that microscope. 
Nevertheless, what he describes is perfectly correct - and not relevant to anything we do here.
Probably the most significant factor is that the capacitors used nowadays are simply too small for the outside "foil" to be significant.
The strange thing about that video is that he pronounces the L in SoLdering Iron.
The first sentence in DVDdougs post says everything you need to know.
The video is quite funny - reminds me of my first contact with a capacitor back in the 70s. And nowadays we are in a 3.3 or 5 volts world. No need to care about the problems anymore that 200-400 volts gave you in a world full of tubes.
michinyon:
The strange thing about that video is that he pronounces the L in SoLdering Iron.
Mmmm.
Must speak English!
That fellow has more gadgets scattered over his workbench than I do! 
Hi,
All he proves about foil caps is that THERE IS NO STANDARD for identifying the lead connected to the outer foil.
He does have a propa CRO, see how beautiful the pattern is. I could watch that bit of the video over and over, and he has more than one!!!!!!! Lucky sod.
Really good thing is if you pull on the leads the CRO won't try and follow you across the bench, like the light weights they have now.
No quantizing steps or digital dots, just instant response. Not, err what did you feed me, let me look at that again, ohh you want that displayed, well you are going to have to go 3 levels down in this menu to turn this parameter ON, then......
Give me a scope with lots of knobs on, a proper GUI, so I can see my alternative settings, and know which one I'm going to incorrectly try and use.
Hey, he pronounces SoLder correctly, not soDDer, like AluminIUM not AlooMINUMM.
Tom.....
By the way CRO= Cathode Ray Oscilloscope.
Hey I Feel Better Now. (Sorry Australian Advert)
He's Canadian.
You can hear it when he's talking "aboot" something.
I can't help getting amazed over and over again when i see apparent Americans thinking that their language and the way they use it, is the only correct way of communicating.
Yes, it's always those "apparent Americans" - "apparent non-Americans" are never provincial.
He's Canadian.
Eh 
MAS3:
You can hear it when he's talking "aboot" something.
I can't help getting amazed over and over again when i see apparent Americans thinking that their language and the way they use it, is the only correct way of communicating.
Maybe it's only east Canada where it's pronounced closer to "a boat" than "a boot".
Do you have any idea how many accents are spoken in the US?
I don't .
It's a large surface, and if i compare it to the surface of the Netherlands where i live, and the number of accents over here (that i know of), it must be a lot.
I don't know about that and really, i don't care.
Others do seem to care, and i can't understand why.
It's not like the message doesn't come across or so.
People need to start accepting that this is an international forum, where the language is English (that's not American) and that that isn't the native language for the majority of the world.
So people trying to communicate in English, even if poor, should not be ridiculed for those attempts.
Sometimes the English is hard to understand and sometimes an automated translation is used (resulting in mostly quite amusing results).
Imagine yourself, as a native English speaking person, to try to communicate in French, German, Dutch or a Scandinavian language.
These are all languages you can find over here on the forum, so easy to have a peek over there to see what that looks like.
I agree a 100% with MAS3. In Europe each country has its funny English accent. However we are used to that. Those who complain about some variations in pronounciation have probably never left the province where they were born.
sis was a little messitch from chermanie