Happy to report that using the Polyscience 300 chamber vacuum sealer, I sealed beef stock today. Thanks to those that offered advice. Success lies in the stock being refrigerated first. I am quite pleased with the unit now that I've been able to do liquids. I've flash marinated, flash pickled, compressed fruit, sealed liquids, and of course vacuum packed foods for storage and/or sous vide. This is a new adventure for me, and I have had fun with it (only having a Food Saver prior to this).