“Is this proper blackout?”

It’s one of the most common questions we’re asked.

But the answer isn’t just about fabric.

It’s about how that fabric is engineered into a blind system.

Because there’s a big difference between a blackout fabric sample in your hand and how that same fabric performs once installed on your window.

Let’s break it down clearly.

Step 1: Understanding Blackout Fabric Levels

Not all blackout fabrics are the same.

Broadly speaking, fabrics fall into three categories:

1. Sheer or Light-Filtering Fabrics (0–30% Light Block)

These fabrics:

• Soften daylight

• Reduce glare

• Provide privacy during the day

They do not block light.

When made into a roller blind, they will still allow visible daylight through the weave.

Ideal for:

• Living rooms

• Kitchens

• South-facing spaces

But not suitable for bedrooms requiring darkness.

2. Dim-Out or Room-Darkening Fabrics (70–90% Light Reduction)

These fabrics:

• Reduce brightness significantly

• Block most visible light

• Create a softer, evening-style glow

However, they still allow some light penetration.

When turned into a standard roller blind, you may notice:

• A faint glow through the material

• Light gaps at the edges

For many households, this is more than sufficient.

But it’s not full blackout.

3. True Blackout Fabrics (Close to 100% Light Block Through the Fabric)

Blackout fabric itself blocks light completely.

Hold it up to a light source and you’ll see no glow.

But here’s where misunderstanding happens.

Blocking light through the fabric is not the same as blocking light around the blind.

And that’s where system design becomes critical.

Step 2: How the Blind System Changes Performance

Now we move from fabric to engineering.

Because the same blackout fabric performs differently depending on the blind system.

Standard Roller Blind (Recess or Face Fit)

A standard roller blind with blackout fabric:

• Blocks light through the fabric

• May allow light around the edges

• Leaves small gaps where brackets sit

In many bedrooms, this achieves 80–90% darkness.

For light-sensitive sleepers or children’s rooms, edge gaps may still be noticeable (particularly in summer).

Cassette Roller Blind

A cassette system encloses the top roll.

This:

• Reduces top light bleed

• Creates a neater finish

• Improves overall light control

It still may allow minimal side gaps unless paired with guides.

Performance increases, but it’s not yet “blockout”.

Side-Channelled Blockout Blind

This is where performance changes dramatically.

A side-channelled blackout blind:

• Locks the fabric into side tracks

• Eliminates side light gaps

• Often includes a bottom seal

This system, combined with true blackout fabric, delivers near-total darkness.

This is typically the best solution for:

• Nurseries

• Shift workers

• Media rooms

• Highly light-sensitive sleepers

It’s also the most engineered solution.

Step 3: Why Window Type Still Matters

Even with a side-channelled system, window shape influences results.

Consider:

• Bay windows

• Velux roof windows

• Out-of-square recesses

• Deep sills

Precision measurement becomes essential.

Light leakage happens in millimetres.

This is why a technical survey matters just as much as fabric choice.

The Common Misunderstanding

When someone says:

“I bought blackout blinds but they’re not blackout.”

Usually what happened is:

• They chose blackout fabric

• Installed a standard roller

• Didn’t account for edge gaps

The product wasn’t wrong.

The expectation was.

Our role is to bridge that gap before installation, not after.

So What Should You Choose?

It depends on:

• How sensitive you are to light

• The room’s orientation

• The window style

• Whether you want full darkness or just dimming

For many homeowners:

• A standard blackout roller is enough

• A cassette system offers a clean, improved finish

• A side-channelled blockout system provides maximum control

There isn’t a universal answer.

There is only the right system for your home.

Why Honest Advice Matters

Light control is one of those areas where overselling leads to disappointment.

We’d rather explain:

• The difference between fabric and system

• What each solution realistically achieves

• Where compromise may exist

Because a well informed decision leads to a calm, finished result and no surprises.

Final Thoughts

Blackout isn’t just a fabric label.

It’s a combination of:

• Fabric density

• Blind engineering

• Installation precision

• Window type

Understanding how those elements work together is the key to achieving the level of darkness you actually want.

And that’s where expert advice makes the difference.