I am selling a deck marker on Ebay:

Item 190630224674

I keep them in heat sealed plastic bags. Well I cut open the bag that this disk
was in to test it. It measures ~16 mR/HR with a calibrated CDV700 standard
configuration with beta shield closed.

Then I tested the bag.

HOLY COW !

I could hardly believe my eyes. With the beta shield open on the X1 scale it
pegged.

On the X10 scale it registered ~1500-2000 CPM

With the beta shield closed just barely on X1.

I held it up to the light to see if there was any evidence of contamination.
It was clear as ever.

The most likely culprit is Radon (Ra-222) that saturated the plastic.

So leaving the bag open for a while, the readings over the next couple of days
decreased, at a rate that is consistent with Radon.

I think that Radon had actually permeated the plastic poly bag to saturation,
and an equilibrium was established over the months that I had the disk heat
sealed in that bag.

So, polyethene bags can serve as well if one whats to snag Ra-222 from a radium
cow.

And what remains as the Ra-222 decays are the daughters.

Steve