Edge Protectors in Monsoon Humidity: Storage and Use

Published 26 October 2026 · By Ranjeet Kumar, Proprietor, Solution Enterprises

Short answer: paper angle boards absorb moisture from humid air, and paperboard loses compression strength as its moisture content rises, so a board stored through a wet spell is weaker than the same board in dry weather. In the monsoon, store boards off the floor and covered, buy closer to when you use them, rotate stock first-in-first-out, and keep wrapped loads out of the rain. Board that has been wetted directly should not go on a critical load.

What humidity does to paperboard

Paper is made of cellulose fibres, and those fibres take up water from the air until they balance with it. This is well studied. A classic Swedish study by Fellers and Bränge found that the compression strength of kraftliner and fluting falls steadily as moisture content rises. It also found that history matters: at the same humidity, paper that has dried down from a wetter state holds more water, and is weaker, than paper that has taken up moisture from a drier state.

Later work points the same way. A 2019 Clemson University study of corrugated boxes tested at humidity levels from 30% to 90% found that moisture content rises with humidity and compression strength falls roughly in line with moisture content. Earlier research at the US Forest Products Laboratory linked humidity that rises and falls in cycles with a significant loss of compressive strength under load. In plain terms: damp weather weakens the board, and repeated damp-dry swings under load weaken it further.

That is also why laboratory strength figures for paper are measured only after samples have been conditioned in a standard atmosphere, as set out in ISO 187. A figure from a conditioned lab sample is not what a board delivers after weeks in a humid shed.

When it matters in India

The India Meteorological Department’s normal dates, revised in 2020, put monsoon onset over Kerala on 1 June, cover the whole country by 8 July, and start withdrawal from west Rajasthan on 17 September. Actual dates move each year, and coastal plants see humid air well outside those months. For a plant or warehouse in the north, the practical window is roughly late June to late September, plus the sticky weeks either side.

Storing boards through the wet months

• Off the floor. On pallets or racking, never directly on concrete, which wicks moisture.
• Away from openings. Not next to dock doors, wash areas or walls that sweat.
• Keep the wrap on. Leave bundles in their packing until they go to the line.
• First in, first out. Old stock sitting at the back takes on the most moisture.
• Smaller, more frequent orders. Less stock on hand means less time in damp air. Our warehouse packaging replenishment guide helps set the rhythm.

On the line and in transit

A board on a load is still exposed. Open trucks, a wait in the rain at a gate, or a container that sweats on a sea voyage can all wet the corners first, because that is where film and strap press the board against the carton. A few habits help:

• Wrap the boards fully under the film so rain does not run behind them.
• Use a top sheet or cover on loads that travel in open vehicles.
• Watch for condensation when a load moves from a cool, air-conditioned store onto a hot, humid dock; water forms on the cold surfaces, corners included.
• Do not load wet boards into a container; trapped moisture has nowhere to go. See how to pack pallets for sea freight containers.

Should the specification change for the monsoon?

Sometimes. If damage claims rise every monsoon on the same lane, there are two options to discuss with your supplier. One is a board with more plies or heavier paper, which gives more margin when moisture takes some strength away — angle board GSM and ply explained shows how those two settings work. The other is a coated or water-resistant outer layer; ask exactly what the coating is and what it resists, because “coated” can mean very different things. Neither replaces dry storage.

Pallets and other paper packaging face the same issue; the wider picture is in packaging for monsoon season in India.

Signs a board has taken on moisture

• It feels cool and soft rather than hard and dry.
• The legs have opened beyond a right angle.
• Outer plies lift at the cut ends.
• The board bends easily by hand where a dry one would resist.

We make paper angle boards in Greater Noida for loads across North India. If your boards struggle in the wet months, tell us the load, the route and how the stock is stored through our contact page, and we can talk through options. Shapes are on the paper angle board page.

Common questions

Does a damp board recover when it dries?

Research on paper shows the link between moisture and compression strength is largely reversible, so a board that was only humid regains much of its stiffness. A board that was soaked, bowed or delaminated does not.

Are plastic edge protectors better in the rain?

Plastic does not absorb water, so it suits loads that are left outdoors. It costs more and is handled differently at the end of its life. We make paper boards only.

Should I use a moisture meter on incoming boards?

A paper moisture meter gives a useful comparison between deliveries and between dry and wet months, even without a fixed pass mark.

Sources

• C. Fellers and Å. Bränge, The impact of water sorption on the compression strength of paper, 8th Fundamental Research Symposium, Oxford, 1985.
• G. A. Brown, Relative Humidity Effects on the Compression Strength of Corrugated Boxes, MS thesis, Clemson University, 2019.
• D. E. Gunderson and J. M. Considine, cyclic humidity and compression creep of paperboard, USDA Forest Products Laboratory, 1986.
• ISO 187:2022, Paper, board and pulps — Standard atmosphere for conditioning and testing.
• India Meteorological Department, revised normal dates of monsoon onset and withdrawal (2020), as reported by The Tribune.

General guidance. Monsoon dates vary each year; follow IMD forecasts for your region. Test any change in board specification on your own loads before adopting it.