I would like to publicly share the following attempt at approximating the weight of a light and heavy base set (first edition or not) blister pack. I know that this is an old thread, but it is well indexed by Google when searching for blister weighing.
TLTR : Blister weighing is not as easy as I thought, read the discussion below.
Note : A light blister has an extremely low chance of containing an holo. A heavy blister has an extremely high chance at containing an holo. In-between is the gray zone where there is a fair chance at opening an holo.
I’m not an expert in pack weighing, I’m not a mathematician and there doesn’t appear to be a consensus. Based on few data points available from public sources, it would appear that the weight range for a pack is around 0.9g and around 1.5g for a blister, meaning that the blister packaging variance is 0.6g. My best effort at computing the average pack weight would be by a weighted average of the (1/3) average heavy and (2/3) average light weights. Here I define “heavy” as having a confirmed holo. I calculate an average of 20.88g. Doing the same with blisters, but with fewer data points and defining “heavy” as 66/100 percentile, I calculate an average of 34.04g. This mean that the blister packaging would add 13.16g +/- 0.3g. This is a very rough calculation, but, interestingly, if I try to compute the same thing using the average of the difference between the heaviest pack and blister and the difference between the lightest pack and blister, I obtain 13.15g. This could be easily confirmed if someone would weigh a bunch of blister packaging after opening them. It appears that the gray zone for a base set pack is between 20.9g and 21.0g, inclusively. Therefor, by my estimations, the gray zone for a blister would be between 33.76g and 34.46g. This is fascinating, because it confirms that weighting blisters is very unreliable and that anything that isn’t in the bottom 1/3 of the weight scale can have an holo. It would define a “heavy” blister as being 34.46g or more. Currently, people appear to anecdotally refer to “heavy” as over 34g or 34.2g. This is because 34.2g would indeed be around the 66/100 percentile, but they fail to account for the increased variance due to packaging.
I mostly used the official spreadsheet for pack weights. For blister weights, the seller of eBay item 333849332436 provided great data (thank you) and I gathered some more from other eBay listings.
I would also like to remind that, although the gray zone is very large, the original owner of a blister box could have weighted each blister and opened them starting with the heaviest and stopped after opening all holos. I do believe that the boxes were limited to 1/3 of holos, that appears to be the consensus. However, since the gray zone is so large, doing so would mean having to open about up to 2/3 of the box. This would be a much more costly endeavor than scanning for bare packs in a booster box. It seems likely that one would stop before opening all holos and, with 24 blisters per box, that may leave a couple behind. It’s also likely and I would say in fact very likely (see the eBayer with 17 of them having a price tag on) that some of the blisters were individually acquired in a big-box store where this cherry picking could prove more difficult.