Re: [Killietalk] Heat sealing of Kordon plastic bags

[Wright Huntley <whuntley at verizon_net>]

Erik Thurfjell wrote:
> I got a question about the heat sealing of Kordon plastic bags. I got a small heat sealer bought in the Philippines. But when I seal off plastic bags they tend to leak. 
>
> Now, Wright Huntley mentioned black vinyl electrical tape. Do you first tape the plastic bag and then heat seal it? Or the opposite or what? 
> I find the Kordon plastic bags fragile to handle and only tested few times so any tips are helpful. Still got 70+ or so to go.
> Sincerely,
> Erik T in Sweden
>   
I use the tape only to attach the bags to the cardboard spacers used to 
keep them flat and separated. The tape covers a minimum of useful 
breather space, while firmly keeping the bags from shifting no matter 
which way the box is turned.

The only heat sealers that work, AFAIK, are the impulse sealers that 
have an adjustable timed burst of heat that is enough to fuse the 
plastic reliably, but not enough to cut the bag through. The AEI ones 
and those similar make a sealed joint that is about 2 mm wide with a 
waffle look. Done right, those seals simply do not leak.

I hold the bag in the jaws of the closed sealer for an extra few 
seconds, to allow enough cooling that the sealed joint is perfectly 
reliable and the softened plastic isn't stretched before it cools.

Some early bags were quite fragile and easily punctured. After that 
first production run, they got very tough, indeed. They still feel soft 
and flimsy, but just try to poke a hole in one with your finger nail. It 
isn't easy. [Cichlid and catfish spines can sometimes poke holes in 
them, though. Somewhere I have an amusing picture of a Tilapia "peeing" 
out both sides of his breather bag.]

Even with a reliable timed-impulse sealer, I hold each bag up to a 
bright window to inspect for any drips from the seal. On the very rare 
occasion when a drip is observed, I just place a new seal adjacent to 
the leaky one and move on. Leaks are usually because I did not get the 
bag 100% flat on the sealer, and a wrinkle then leaks.

I like each bag to have three sealed compartments. Two each are for a 
fish and water, and the last is for a label (in air) that stays dry and 
is hence usable at the other end.

Microfiber cloths are excellent for mopping up spills and stuffing any 
empty spaces in the box to soak up any leaks and prevent shifting of the 
contents.

It helps to cut the cardboard spacers to be an almost snug fit in the 
box. Add two long double tapes (sticky sides together) to the bottom one 
as handles for lifting the whole stack out when unpacking.

Wright

-- 
"The best argument against democracy is a five-minute conversation with the average voter."   --  Winston Churchill 

Wright Huntley - 805 Valley West Cir., Bishop CA 93514 
whuntley at verizon_net 760 872-3995. Cell 760 937-2276

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