by Stephanie Warwick Stephanie Warwick No Comments

I have been employed in the packaging industry for many years (I’d rather not  say how many!) and have been promoting the benefits of barrier foils over other climatic protection measures for most of them. Yet it never ceases to amaze me that there are still people in the same industry who have not yet grasped the importance and cost effectiveness of foil laminate bags for the prevention of corrosion and moisture damage.

I was asked recently by an export packaging company to calculate how much desiccant is required in a tar paper lined timber case to protect the contents from moisture ingress for 6 months in the tropics.  They did not intend to use a barrier bag around the expensive, moisture sensitive product within the case !

So once again I had to deliver the age old message, which is:

 1) Silica gel and activated clay desiccants cannot perform effectively in mopping up moisture unless they are used within an enclosed environment , otherwise they quickly become saturated and cease to function.

 2) As long as the barrier bag’s water vapour transmission rate and surface area are known, the amount of desiccant required per month can be accurately calculated, using the formula in BS1133 section 19. This is detailed on our website :

 3) A polythene bag 125 microns thick will allow the ingress of 4 grams of moisture vapour per square metre of it’s surface area, per day!  Foil Bags

 4) A bag made in a typical foil laminate from Protective Packaging’s range will allow less than 0.05 grams of moisture vapour per square   metre per day to migrate through it. This means you need 80 times less expensive desiccant within the bag, saving a lot of money, plus there is no need for any lining within the case except under the lid.  Our cross woven case lid liner is very strong and effective in preventing rain water ‘puddling’ on top of the foil bag.    

Paul Walker

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