Being in private practice, we are always on the lookout for glass jars as secondary containers that are suitable to hold the common solvents and chemicals that we work with (eg acetone, xylene, alcohols, adhesives). Often these jars are only available in bulk quantities or at chemistry lab prices. They can also come from overseas, adding to the cost.
The best jar is one that:
- has a flat bottom
- you can fit your hand or a cleaning sponge into
- has smooth inner and outer walls (i.e. is not angled and has no designs)
The glass isn’t really the problem, it’s the closure. These have to be solvent resistant. Manufacturers may claim that is the case, but, in reality, they are not compatible.
Why not just use a jam jar or a preserving jar? We try not to use containers that have had food residues in the past, both because of tikanga in working with taonga, as well as, the closures are not suitable.
In an effort to trial something suitable, we contacted Arthur Holmes to trial some options. We like to use 250mL or 500mL sized jars for our secondary chemical mixtures as we tend to make them fresh and only use small quantities. For solvent storage, we use the larger reagent jars from Lab Warehouse in 1L size.
Our trial used the Food Screwtop Jar from Arthur Holmes. They are nice and tall and fit in our shorter chemical storage cabinet shelf. They are reported as being polypropylene.
This type of jar comes with two closure options: ‘foodseal’ (plastic) and aluminium.
Both can be used with a wadding insert (described as polyethylene/LDPE) that assists in ensuring a tight fit.
Experiment
For this experiment, we only trialed acetone, one of the more aggressive solvents for plastics and one that has a high evaporation rate (so any leaks to the closures would have been noticeable in a short period of time).
Disclaimer: This is by no means an analytical chemistry test!
For the wadding (described as a polycel liner), we left the wadding soaking in acetone for 24 hours to see if there was any visible changes or physical changes (noted by flexing and attempting to rip them).
For the lids, we left acetone soaking in them 24 hours to test whether the material would react.
To test the efficacy of the seal, we measured the amount of acetone left in the jars after a set amount of time to see if any had evaporated. We did this by volume rather than weight (because our scale was not sensitive enough).
We tested the foodseal on its own and the aluminium with the wadding and without the wadding.
One weakness in this trial, of course, is that we may not have gotten all the acetone out when we poured it into the graduated cylinder.
Results
Wadding
- Firstly, we tested the wadding to see if it would react to the acetone.
- Results: No reaction. There was no change to the integrity of the wadding. Nor was there any discolouration to the acetone that may show dissolution of the plastic.
Aluminium, reaction to acetone
- We did not predict the aluminium would change; however, sometimes there can be coatings that are unseen or treatment processes to the metal that may react.
- Results: No reaction.
Aluminium with wadding, leakage rate
- Started with 30mL of acetone
- After 24 hours: 29mL
- After 48 hours: 28mL
- After 72 hours: 28mL
- Results: Lost 2mL in 3 days
Aluminium without wadding, leakage rate
- Started with 28mL of acetone
- After 24 hours: 27mL
- After 72 hours: 25.5mL
- Results: Lost 2mL in 3 days
Foodseal, reaction to acetone
- Results: No reaction. Nor was there any discolouration to the acetone that may show dissolution of the plastic.
Foodseal without wadding, leakage rate
- Started with 30mL of acetone
- After 24 hours: 29.5mL
- After 48 hours: 29mL
- After 72 hours: 28.5mL
- Results: Lost 1.5mL in 3 days
Summary
This very restricted experiment has shown that there is no reaction between acetone and the plastic or aluminium materials, making it suitable for secondary chemical storage. There seems to be a better seal with the foodseal lids. Perhaps these combined with the wadding inserts create an even tighter seal.
Next up, we’ll trial some other solvents!
Artifact Preservation 