IELTS Writing Task 1 Process Diagram: Structure + Band 8 Sample
Process diagrams look intimidating because there is no data to compare. Once you know the tense, the voice and the sequencing pattern, they are the most predictable Task 1 question type.
What a process diagram is testing
A process diagram shows how something is made, recycled, or produced — a manufacturing sequence, a natural cycle, or a set of stages. There are no numbers to compare, so examiners focus on three things: can you identify the beginning and end of the process, can you divide it into logical stages, and can you describe each stage accurately in sequence. This is a test of controlled description, not of vocabulary creativity.
Tense and voice: the rule that fixes half your errors
Most process diagrams have no dates, so use the present simple passive: 'the glass is collected', 'the mixture is heated', 'the bottles are packed'. Passive voice is correct here because the doer is unimportant or unknown — the process itself is the subject. If the diagram shows dates or a historical development, switch to past simple passive. The single most common band 6 error in this question type is describing the process in the active voice with an invented subject, for example 'workers collect the glass' when no workers appear in the diagram. Our grammar guide covers passive forms if you need a refresher.
The 4-paragraph structure
Paragraph 1: Introduction — paraphrase the question and state what the diagram shows. Paragraph 2: Overview — the number of main stages and the start and end points, with no stage-by-stage detail. Paragraph 3: The first half of the process, stage by stage. Paragraph 4: The second half, through to the finished product. If the diagram is a cycle rather than a linear process, say so in the overview and describe the loop, noting where it returns to the beginning.
Sequencing language
You need a clear sequence without repeating the same connector. Use: 'first', 'at the first stage', 'once the glass has been sorted', 'after this', 'the next stage involves', 'following this', 'subsequently', 'at this point', 'finally'. Note the grammar: 'once' and 'after' take a present perfect or present simple clause, while 'following this' stands alone. Vary between sentence-initial connectors and mid-sentence ones so the answer does not read like a numbered list.
Common mistakes to avoid
Mistake 1: inventing details that are not in the diagram, such as machinery, workers or durations. Mistake 2: skipping or merging stages, which lowers Task Achievement because the summary is incomplete. Mistake 3: writing a conclusion — Task 1 needs an overview, not a conclusion. Mistake 4: describing the diagram itself ('there are six boxes and some arrows') rather than the process. Mistake 5: mixing active and passive voice randomly, which reads as inconsistent control.
Sample band 8 answer
The diagram illustrates the process by which used glass bottles are recycled into new glass products. Overall, the process consists of six main stages, beginning with the collection of waste glass from households and ending with the distribution of newly manufactured bottles to retailers. First, used bottles are placed in recycling bins by households and are then collected by truck. The glass is subsequently transported to a treatment plant, where it is washed and sorted by colour into green, brown and clear glass. At the next stage, the sorted glass is crushed into small fragments known as cullet. The cullet is then melted in a furnace at a very high temperature, after which the molten glass is poured into moulds to form new bottles. Finally, the finished bottles are packed and delivered to supermarkets for sale.
Frequently asked questions
Should I use passive voice in a process diagram?+
Yes, in most cases. If the diagram has no dates, use the present simple passive — 'the glass is collected'. Passive voice keeps the focus on the process rather than on an unnamed person or machine.
How do I write an overview for a process diagram?+
State how many main stages there are and where the process begins and ends. For cyclical processes, say that the process is a loop and note where it returns to the starting point. Keep all stage-by-stage detail out of the overview.
Can I add information that is not shown in the diagram?+
No. Everything you write must come from the diagram. Inventing workers, equipment or timeframes lowers your Task Achievement score because the summary is no longer accurate.
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