Preparing a Quality Waterproof Geocache
Recently, a number of airtight locking plastic containers have appeared on the market ostensibly intended for food storage. These containers - including the infamous "Lock-n-Lock" - have gained notoriety as some of the most revered geocache containers, second only to the venerable ammo box. These small but amazing little plastic boxes do a great job, and provided that they aren't subjected to extreme stress or physical abuse they will provide a secure and watertight home for your geocache goodies for years with minimal maintenance.
While it's perfectly acceptable to take a container straight from the store shelf and hide it somewhere, I personally prefer adding a personal touch. Not only will it be appreciated by most geocachers that find your cache but you'll feel a sense of pride in your geocache hides.
Most containers I encounter are either unpainted or if they have been painted, the paint has chipped off due to either the use of low quality paint, inadequate surface preparation, or both. As outlined below, a little time and a few dollars will turn any quality plastic container into a high-quality geocache that will stand the test of time and the elements.
Step 1 - Preparation
Choose a good container. Several companies manufacture similar containers, get what is available to you in your area. I have had great success with a brand called "4-side-locked" (I haven't been able to find the manufacturer's website) which I picked up on sale at a local supermarket for about $2.00 (Canadian) for the 300ml version. I have also had good success with the "Lock-n-Lock" brand, as well as in Australia and New Zealand Sistema makes excellent containers for this purpose as well which can be found on sale for a few dollars.
Preparation before painting is an oft-overlooked but nonetheless very important step.
Remove any stickers from the outside of the container. If you are using Sistema containers, try and buy a bulk pack as these usually don't have any stickers on the containers themselves - a huge timesaver. If your container has stickers, you'll need to remove them and depending on what sort of adhesive was used will determine what you need to use. Sometimes soap and water will work, but you'll usually need to use something a lot stronger. However, as a general rule of thumb try and avoid using petrolium based cleaners (kerosene, lighter fluid, etc) as they tend to leave an oily residue that is very difficult to remove and paint won't adhere to it. If you have no choice but to use a petrolium based solvent, you'll need to take extra precautions to remove any residue before proceeding.
I have had good success with Isopropyl (aka rubbing) alcohol, which can usually be purchased for a few dollars for a bottle. Not only is it great at removing most label types, it can also be used to clean up after using a petrolium based cleaner. It also quickly evaporates, it's very smelly and very flammable so use only in a well-veltilated area, keep away from ignition sources, avoid breathing the fumes and wear gloves. However, it works phenominally well at removing many adhesives, as well as oils left behind from touching the container so it's great to give the container a wipe-down with an alcohol soaked cloth just before the painting step.
Some people recommend running the containers through the dishwasher to remove any residual compounds from the manufacturing process. This step is purely optional and I have had great success both with and without performing this step. If you do decide to run your containers through the dishwasher, I suggest removing the silicone band from inside first, if possible, as dishwasher detergents can be pretty nasty and we don't want this waterproofing element to break down - it's best to avoid doing anything that may inadvertently shorten it's lifespan.
I find that usually just a good scrub in soapy water is enough, but you don't need to worry about the cleaning process until after the next step.