Footwear Manufacturing Capabilities - Jiangsu

Jiangsu – A centre of footwear manufacturing excellence

The Gumboot Manufacturing Process

The building of hand-made natural rubber gumboots is a very labour and capital-intensive process requiring multiple handling of most of the components.  Most Skellerup gumboot styles have in excess of 19 individual components for each half pair of boots.

There are 7 major steps when manufacturing a pair of natural rubber gumboots (and several other ancillary ones). They are as follows: -

1. Mixing. The natural rubber is combined with other ingredients such as carbon black, oil, fillers and curatives and mixed either in an enclosed mixing machine or on an open top mill. Extreme accuracy is required when weighing out the ingredients at this stage to ensure the desired physical properties of the mixed compound is achieved.

Once the compound has been mixed it is stored to allow it to ‘settle’. The compound is tested to ensure it complies with the pre-determined specifications.

From the store the uncured rubber is issued to 4 pre processing departments prior to the assembly stage.

(Typical components making up a Skellerup Gumboot)

(Canvas being fed into a Calendar to make either Skim or Friction)

2d. Skim and Friction Calendering. Skim is the canvas lining inside the gumboot. It has a layer of rubber skimmed onto the surface that makes it form a very strong bond to the other rubber components. Friction is canvas that has had rubber forced into the weave of the canvas and is used as a reinforcing layer internally in most of Skellerup gumboot styles. Unlike in Upper Calendering, a roll of canvas is fed into the first 2 rollers where either the rubber is ‘skimmed’ or ‘frictioned’ onto or into the canvas. The Skim and Friction is then rolled onto the drums. An assortment of components is then ‘clicked’ out from the continuous rolls of skim or friction using a clicking machine.

(Some of the hand tools used when making natural rubber gumboots)

3. Boot Assembly. The assembly chain is a long narrow table with a chain revolving around the outside with the lasts sticking up in the air with 22 people standing on station each doing a particular operation. Every pair of gumboots is assembled on a ‘last’, and is done by laying on the successive layers of skim, friction, uncured upper rubber components etc to the last and finally a sole and heel is affixed. Because the rubber is uncured it is sticky so once it is laid in the desired position, it stays there.

4. Vulcanisation. The lasts are removed from the assembly chain and packed on a boot trolley and pushed into a large oven called a vulcaniser where the boots are cured by heat and under pressure.  Once the vulcanisation is complete the boot trolleys are removed and the gumboots are pulled off once the aluminium lasts have cooled down.

• Flex Resistance: the boots can flex several million times without showing any surface cracking.
• Canvas Lining (Skim): all Skellerup gumboots are made with a heavy-duty canvas lining that gives the entire boot its firm structure and strength. It also ensures that the rubber components stuck to it won’t separate unlike most cotton sock-lined gumboots.
• Internal Canvas Reinforcing (Friction): a unique design feature to Skellerup gumboots that assist with the structure of the boot but more importantly protects that gumboot from tearing and puncturing against sharp objects.
• Sole Abrasion: the soles won’t wear out quickly.
• Ultra Violet Protection: our boots are made including anti ozone protection to guard them against New Zealand’s harsh sunshine which degrades rubber quickly.
• Fitting: All Skellerup gumboots are made to fit New Zealanders specific foot shapes, being typically wider than normal.
• 100% Inspection: Every pair of Skellerup gumboots is hand inspected in New Zealand prior to despatch.

Do You Know?

The first rubber boots were made by South American Indians who poured latex from Hevea Brasiliensis (rubber tree) over their legs and feet.

MY WONDROUS “SKELLIE” GUMBOOTS
(submitted by a satisfied Skellerup customer in 1995)

In the year of ‘59
Two great possessions became mine:
A lovely bride I gladly sought,
New “Skellie” gummies I also bought.

“Now listen mate”, the salesman said
“These will last you til you’re dead”.
“What, three score years and ten?
You really must be joking then”.

Since that day, in many places.
I’ve worn those boots – without their laces;
Digging gardens, mowing lawns
Battling floods and netting prawns.

A dozen cars have come and gone,
Four kids now grown have all been born,
Twelve houses we have occupied –
And still those boots remained my pride!

The years have passed now six and thirty;
My Skellerups were often dirty.
What now I see it makes me groan –
Across the heel two splits have grown.

The bride I wed she loves me still,
But my size 10’s with water fill
Each time I put them on my feet
And struggle out into the street.

The soles are strong, the heels quite worn,
The uppers firm – just slightly torn;
No longer do they keep out water
To keep my feet dry like they ‘orter’.

Although I’ve cherished them all these years
And to lose them will bring tears
I’d be prepared with them to part
To give your museum-a gumboot start!