Defects

 Cause

Corrective measures

Pin head bubbles

Pre-coagulation

Use of dirty utensils

Latex contamination with rain water

Use of excess acid or too high concentration

Insufficient dilution

Addition of Anti-coagulants in the field

Use of clean utensils

Prevention of the contamination

Use of correct amount of diluted acid (1%)

Correct dilution of latex

Medium size bubbles

Fast coagulation

Insufficient dilution

Insufficient skimming of the surface

Use of correct amount of diluted acid (1%)

Correct dilution of latex

Complete removal of froth after addition of acid

Large bubbles

Too high drying temperature

High thickness of sheets

Maintain the correct drying temperature

Use sheets with recommended thickness

“Reaper marks”

Not turning sheets daily

Use of dirty reapers

Turn sheets

Use of clean reepers

Dirt

Improper straining of latex

Rubbing the sieves too vigorously during straining

Use of bad quality water

Un-covered coagulation

Un-cleaned smoked houses

Proper straining of latex

Avoidance of the causing mal practices

Use of pure water after strain through a fine cloth

Prevention of falling foreign materials onto latex

Maintain the cleanliness of smoke house

Dull colour

Enzymatic discolouration

Insufficient washing  of sheets

Smoking of insufficient drained sheets

Prolonged smoking

Unevenly thick sheets

Add sodium bisulphate solution

sufficient washing of sheets

Adequate dripping of sheets

Avoidance of over smoking

Use sheets with recommended thickness

Rust

Insufficient washing of sheets during milling  Prolonged dripping of wet sheets

Restricted  air flow inside the smoke house

Too low temperature in the smoke house

Use of badly worn-out mills

Washing the sheets properly

Shorten the dripping time

Maintain adequate air flow inside the smoke house

Maintenance of  the correct drying temperature

Maintenance of machines in good condition

Glossy surface

Use of wet firewood

Use of certain firewood types such as coconut shells, coconut husks and paddy husks

Use of dry firewood

Avoidance of such firewood types

Mould growth

Delay in drying

Storage of sheets under high humidity without adequate ventilation inside the store room

Insufficient removal of non-rubber

Excessive use of sodium sulphite/bisulphite

Dry the sheets without delay

Store dried  sheets with proper arrangements

Maintain a good ventilation in the store room

Adequate washing

Use of recommended level of theses chemicals

Greasy sheets

Insufficient washing of sheets

Inadequate dilution of latex

Sufficient washing in running water

Dilution of latex at recommended DRC

Tackiness

Use of excess of sodium salts

Drying at high temperature

Contamination with oil and grease on rollers

Contamination with copper ions

Use of the chemicals in correct doses

Maintain the correct drying temperature

Prevention of latex contamination with oil and grease

Prevention of latex contamination with metal ions

Thick edges

Insufficient dilution of latex

Use of out of shaped pans

Placing coagulating pans on non-horizontally

negligence during milling

Diluting the latex in to recommended level

use of pans of correct dimensions and shape

draw more attention on milling

Flat roller marks

In sufficient dilution

Use of excessive amounts of acid

Using of worn out diamond rollers

Correct dilution of latex

Use of accurate amounts of properly diluted acid

Use of good rollers

Tar spots

No ceiling in the smoke house

Poor ventilation in side the smoke house

Introduction of a V-shaped ceiling

Maintain a good ventilation in the store room

Ash particles

Using a smaller baffle plate

No baffle plate

Careless operational practices

Fixing a baffle plate of correct measurements

Adequate ventilation

Appearance

Lack of attention on the recommended manufacturing process

Pay proper attention to all steps of manufacturing process