[Harp-L] Nail polish and bubbles

[Vern]

> On Jan 21, 2019, at 10:32 AM, Rick Epping <rickepping at xxxxx> wrote:
> 
> ……….I don’t think there’s really any question that more air leaks through the offset of the opposing, or opening reed than through the back third of the primary, or closing reed.  It seems obvious to me and Vern’s bubble test only confirms it. However, it also seems to me that more is at issue here than simply how much air is leaking into or out of the reed cell while a reed is playing.
> 
> Free reeds produce sound in a manner similar to that of a pneumatic siren,
> by repeatedly interrupting an airflow, creating alternating rarified and
> compressed pulses of air.  The more effective a reed is in rapidly and
> completely cutting off the airflow that passes through its slot, the more
> defined are these air pulses and the better the reed will perform.  Air
> leakage around the opposing reed will affect airflow within the reed cell
> but not perhaps the air pulses exiting the slot of the primary reed.  A
> harmonica reed, when properly voiced, enters its slot along its entire
> length at the same moment, causing a rapid interruption of
> airflow.  Sealing the gap at the back of a reed should help to achieve a
> more complete interruption of airflow through the primary reed's slot.
> Conversely, a reed with a curvature such that the middle of the reed passes
> through the slot before the tip does, or vice versa, will have a relatively
> poor signal-to-noise ratio – the noise being that breathy sound that
> accompanies a badly adjusted harmonica.  Because the airflow is never
> completely and/or is not rapidly interrupted, the reed will perform poorly
> in terms of tone, response, bending and overblowing.

I agree with most of the above.  Brendan based his claim on leakage and that is what I questioned.  Because his treatment affects only the least active third of the reed and slot, I infer that it will have a minimal, perhaps imperceptible, effect.

I did not question reed voicing in general…only nail polish on the rivet third of the slot.

This is what I would expect of embossing:
- More frequent jamming of the reed by particles of dust, hair and food.
- A slight (maybe imperceptible) increase in the energy in high overtones resulting in a more shrill tone. These changes could be in the “dog-whistle” range above the frequencies that old men can hear.
- A slight (maybe imperceptible) improvement in reed efficiency.
- Raised expectations resulting in subjective perceptions of improvement. 

Can you state values for typical clearances before and after embossing?
My guess is that they could be about .0015” and .0005”

Vern