Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, Richard <metal@...> wrote:
 
> Excellent post Bill....good detailed report.
> 
> I'll note only one thing:  you're either not accounting
> for emissivity in your optical temp-measurements; or
> you were measuring a broken household iron.
> 
> The temps you reported were at or below the boiling
> point of water.  The bottom surface of the normal 'iron'
> gets far hotter than that.  One doesn't need a thermometer
> for it even...just crank up an iron for a few minutes, then
> turn it over and sprinkle water on it... <g>

I had considered the boiling point issue since I know both irons do
produce steam.  However, I had assumed (dangerously) that this was due
to higher temps inside the iron because of closer proximity to a
heating element of some kind. I was also aware that surface emmisivity
was a factor since I'd read about it in the instructions (yes, I
actually read instructions... sometimes), but I didn't think (for some
reason) that it would have _that_ much of an effect.  

However, now that you've made me consider it, the area of the travel
iron that gave a considerably higher temperature reading was a
darkened area that I assumed (there's that word again) was darker
_because_ the higher temperature at that point on the surface had
discolored it.  That very well may have been the case, BUT the
emmisivity was also higher because the surface was darker in that
area!  And the lighter surface of the household iron caused even more
of an emmisivity-related error and, thus, lower temperature readings
than the travel iron. Duh! Wake up Bill!

Well, discard that "too-cold iron" theory and tack any problems with
the iron method up to bad technique alone (as someone said earlier). 
In the end, the oven method appears to be useful in producing quick
and reliable transfers using a cheap laminators without having to
perfect one's technique in the use of a hand iron.

Bill