PTE · Describe Image

Traditional and Modern Indigo Dyeing: PTE Describe Image practice questions

4 original Describe Image questions. Question 1 is free to record, play back and compare with a sample answer right here; log in free to practise the rest in the BandLadder app.
  • 4 questions
  • Question 1 free, no login
  • PTE Academic and PTE Core
1

Natural Indigo Extraction Process

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Look at the image below. You have 25 seconds to study it, then 40 seconds to describe in detail what it shows.

Stages of Natural Indigo Extraction. Stage 1: Harvesting fresh indigofera leaves. Stage 2: Fermenting leaves in water vats. Stage 3: Aerating the liquid to induce oxidation. Stage 4: Settling and collecting indigo paste. Stage 5: Drying paste into solid pigment blocks.

Stages of Natural Indigo Extraction
  1. 1.Harvesting fresh indigofera leaves
  2. 2.Fermenting leaves in water vats
  3. 3.Aerating the liquid to induce oxidation
  4. 4.Settling and collecting indigo paste
  5. 5.Drying paste into solid pigment blocks

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Questions 2–4

Look at the image below. You have 25 seconds to study it, then 40 seconds to describe in detail what it shows.

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2

Synthetic versus Natural Indigo Yields

Annual Textile Dye Production by Source (thousand tonnes). Synthetic Indigo: 1980 20, 1995 45, 2010 70, 2025 85. Plant-derived Indigo: 1980 15, 1995 10, 2010 5, 2025 8.

Annual Textile Dye Production by Source (thousand tonnes)
0204060801001980199520102025
  • Synthetic Indigo
  • Plant-derived Indigo
View the data
1980199520102025
Synthetic Indigo20457085
Plant-derived Indigo151058
3

Global Indigo Dye Consumption Shares

Global Indigo Consumption by End Use (%). Denim Manufacturing 72, Traditional Craft Textiles 14, Medical and Chemical Reagents 9, Printing Inks and Paints 5.

Global Indigo Consumption by End Use (%)
  • Denim Manufacturing: 72%
  • Traditional Craft Textiles: 14%
  • Medical and Chemical Reagents: 9%
  • Printing Inks and Paints: 5%
View the data
CategoryValue (%)
Denim Manufacturing72
Traditional Craft Textiles14
Medical and Chemical Reagents9
Printing Inks and Paints5
4

Fermentation Vat Temperature and Alkalinity

Indigo Vat Performance Under Varying Conditions. Columns: Vat Type, Optimal Temperature, Required pH Level, Reduction Time. Natural Sukumo, 28-32 C, pH 10.5-11.5, 7-10 days. Quick Chemical, 45-50 C, pH 12.0-13.0, 30-45 minutes. Fructose Vat, 35-40 C, pH 9.5-10.5, 2-4 hours. Iron Vat, 20-25 C, pH 8.5-9.5, 1-2 hours.

Indigo Vat Performance Under Varying Conditions
Vat TypeOptimal TemperatureRequired pH LevelReduction Time
Natural Sukumo28-32 CpH 10.5-11.57-10 days
Quick Chemical45-50 CpH 12.0-13.030-45 minutes
Fructose Vat35-40 CpH 9.5-10.52-4 hours
Iron Vat20-25 CpH 8.5-9.51-2 hours

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