I buy the brand-name CA from the hobby shop because ounce for once or gram for gram, it works out to be much cheaper than even the no-name dollar store variety! I buy BSI CA (usually rebranded with the store's name) in 2 oz. bottles. 2 ounces is equivalent to 56.7 grams. I pay $8.99 per bottle. This works out to $0.16 per gram.
Dollar store CA usually comes in tiny squeeze tubes, with several of these tubes blister-packed onto a card, for which the price is $1. Collectively, the set of tubes contains maybe 4 grams of CA. (A rough but generous estimate.)
In order to buy an amount equivalent to a 2 oz. bottle, you would have to buy 14 cards of the dollar store variety. So you would pay $14 for the same amount of CA as the 2 oz. BSI bottles contain. This works out to around $0.25 per gram.
When I used to buy those little squeeze tubes of superglue, I would get just one use out of the tube. I would often use about half of the contents on whatever I was working on, and then recap it and try to save the rest for another time. But the remainder would always harden in the tube before I got to use it again. So out of a dollar store pack of superglue that contained a total of something like 4 grams of glue, I would actually get to use something like 2 to 3 grams. So my cost per gram was even higher than the previous calculation.
The hazard with buying CA in 2 oz. bottles like I do is that it can prematurely harden in the bottles just as easily as it does in the little tubes. And if the bottle hardens up before you get to use even half of it, then you lose a whole lot more CA than you do in the little tubes. I take three precautions to prevent that from happening.
- Once it has been opened, keep the bottle sealed in a zip-lock bag when it is not in use.
- Never unscrew the cap and dip something into the bottle to pick up a little glue. You run a very great risk of introducing contaminants into the glue when you do this, especially water vapor. Water vapor is the catalyst that hardens cyanoacrylic adhesive, so you want to do everything possible to keep ambient water vapor from getting into the bottle. If I want to pick up a quantity of CA on an applicator before transferring it to my model, I squeeze a small amount onto a plastic plate and then pick it up from there. I also keep the outer cap on the bottle whenever possible, which means that it is on all the time, except when I am actually dispensing glue from the bottle.
- Keep your CA accelerator and your bottles of CA well-isolated from each other, and don't apply the accelerator in the presence of a bottle of CA, even if the bottle is capped. I occasionally use BSI Insta-Set, which is their accelerator, to quickly set Maxi-Cure CA (BSI's version of extra thick and slow-curing CA). I bought a couple of small pump spray bottles of it and a large bulk container of it. I store them in a sealed container (a recycled coffee can with a plastic snap lid) at all times except when I am actually using it. I keep the container in the room across the hall from my workshop, so it isn't even in the same room as the CA.
I'm a bit of a fanatic about this next procedure, so bear with me. When I anticipate that I am going to use Insta-Set on my model, the first thing I do is get the coffee can and take it outside and leave it on my deck. Then I go back to my workshop, apply the CA, cap the bottle, and then take my model out to the deck. Then I take the accelerator out of the coffee can and apply it where needed on my model. In other words, I apply it outdoors, well away from where I keep my CA. Then I leave the model out on the deck for at least an hour before bring it back inside to my workshop. On my way back into the house, I stop and wash my hands with soap and water before reentering my workshop room. I know, it sounds like I am working with hazmat. But Insta-Set isn't hazardous to anything but uncured CA. And even a couple of stray droplets in the air in the same room as the CA can eventually make their way into the bottle, and if that happens, it's game over.
By following these precautions, I have kept bottles of CA good and usable for almost 2 years after I first opened the bottles. I don't know how long the CA can ultimately be kept this way, because I always use it all up within anywhere from a few months to a couple of years after I open the bottle. But by preserving the CA, I also preserve the money I saved by buying it this way.
MarkII