Local store has Sterilte ClearView storage bins for sale at really cheap prices. A look at Sterilite's website says it's products are made of polypropylene and polyethylene and are acid-free and PVC free. A more detailed description is given at: http://www.sterilite.com/general_info.html My question: assuming I add desiccant, can I trust my coins to be safe in these? Thanks in advance, Brian
The plastic container will not cause any problems. Dessicants will help control the moisture, but environmental gases can still enter ( as container not air tight ) over the long run. You can take some copper ( I refer the modern copper clad US cent ) coins and rough them up with scrubbers until they are very bright and cleaned, and toss them in the box. The environmental gaseswill react with this "fresh" copper before reacting with the other coins, which all have a minor protective patina layer. When the sacrificial fresh copper coins turn toned or brown doing their job, remove them and rescrub and return. Very cheap and effective. Jim
Personally I use #5 polypropylene. It has almost no leaching or breakdown of materials. #2 high density polyetehylene is good but eventually from what I understand the ethylene part can emit non toxic gases but it takes decades and some high temps so unless you live in the southwest it should be fine. This plastic may also explain why you would need the cent trick from desertgem. I would only avoid #3 PVC, #4 Low Density Polyethylene (aka cleaners bags, grocery bags material) allows gases in and out. #6 plastic which is polystyrene(foam plates) very porous and toxic if melted and #7 plastics (you never know what is in them). Just to be thorough #1 pete is to my knowledge only used in construction and food container applications no storage bins are made from it.
Local store has Sterilte ClearView storage bins for sale at really cheap prices. A look at Sterilite's website says it's products are made of polypropylene and polyethylene and are acid-free and PVC free. A more detailed description is given at: http://www.sterilite.com/general_info.html My question: assuming I add desiccant, can I trust my coins to be safe in these? Thanks in advance, Brian Reply: You can trust Polypropylene with your coins. The benefit of Polyethylene is it's high tensile strength, chemical and dimensional stability, reflectivety, gas and aroma barrier properties, and electrical insulation over Polypropylene's lower cost. Also the acronym for myral is BoPET or just PET.
While putting "bared" copper cents in a box with coins is helpful in scavenging reactive gases like hydrogen sulfide, the process depends on the reactive gas molecules hitting and reacting with the sacrificial coin or coins before they hit the more valuable coins. A better way is to surround the valuable coins with reactive copper so that the reactive gases are forced to contact the sacrificial copper before they can ever reach the coins. This could be done with copper plates, foil or screen, but the easiest way is Lighthouse Intercept boxes. This technology was patented by Lucent, and the patents can be read online. The lining of the boxes consists of copper particles embedded in conductive carbon. Although the patents have expired, I think only Lighthouse markets the technology for coin protection. If you are concerned about the Lighthouse box lining becoming exhausted, you could put a shiny penny inside the box as an indicator. Depending on the other components mixed with copper, presence of surface contaminants, temperature, and humidity, it can darken due to reaction with oxygen alone. So, a change in color of an indicator cent doesn't necessarily mean it's reacted with nastier gases, like hydrogen sulfide. Generally, methods of getting rid of oxygen (inert gas purging, vacuum, oxygen absorbers) are considered too onerous or expensive for most collectors to use. If you put items that can generate hydrogen sulfide and other nasties inside the container with your coins, attempts to scavenge them before they reach your coins will be of little use. Common villains are some paper and cardboard products. Cal
I agree that pure polyethylene and polypropylene are safe for coins. However, for food storage, some plastic containers made of these compounds are labeled as antimicrobial. This means there is some additional compound on the surface of the plastic. Avoid plastic bags and containers labeled "antimicrobial" for coin storage. Cal
Would the polyethylene bags have antimicrobials or additives, It says waterproof, strengthened and antioxidant ? Doesn't specifically mention anything though.
I haven't seen PE bags that state they are antimicrobial, only rigid containers, but they might exist. Bags labeled antioxidant are most likely simply referring to the exclusion of air (and the oxygen it contains), not a chemical coating. I've never had a problem with zip-lock PE baggies. Avoid vinyl zip-lock baggies. Cal
Hey Cal, Thanx for that, Grip seal Poly bags should be okay then as well ? The boxes are from - https://www.reallyusefulstorageboxes.co.uk/PBCPPlayer.asp?ID=1623952 And it states on thier website All Really Useful Boxes are manufactured using Polypropylene. All Really Useful products have a working temperature of -15°C to +80°C. Boxes are not made in a sterile environment, so they're therefore NOT 'food grade'. The polypropylene used to manufacturer Really Useful Boxes is however safe to store food and therefore the boxes are 'food safe'.
I was using zip-lock as a generic term, but it's actually a trademark. So other manufacturers used similar terms, like grip-seal. They're all OK for coins as long as they are PE (not vinyl). The PP boxes should be fine too. Cal
Hey guys, I cant seem to find HDPE grip lock bags here in the UK or Polypropelene ones that I can use for my low grade individual coins. By default I've using double bagged LPDE 50 micron PE grip seal bags but I'm wondering about the long term affect these my have on my low grade coins ($5-10) cupro, brass, nickel and silver. Also if there proximity to my lighthouse capsuled coins as well. If anyone has any thoughts or suggestions please let me know. Cheers Oddity
LDPE (low density polyethylene) is just as inert as HDPE. It's more flexible and not as tough. Most polyethylene bags, grip-lock or twist-tie, are made of LDPE. Cal
