One of the most common questions in plastic whitening is:
How much optical brightener should be added?
There is no single dosage that works for every plastic.
The required amount depends on the polymer type, optical brightener grade, initial color, pigmentation, product thickness, processing conditions and other additives in the formulation.
For this reason, the most effective approach is not to look for one universal dosage, but to determine the optimum dosage for the actual formulation.
1. Why Is There No Universal Optical Brightener Dosage?
Optical brighteners are highly efficient fluorescent additives and are normally used at relatively low concentrations.
However, different formulations can require very different addition levels.
Archroma’s technical data for plastic optical brighteners demonstrates this clearly. Recommended concentrations vary according to both the optical brightener grade and the polymer system. For one grade, published application levels range from approximately 10–20 ppm in transparent plastics to 50–250 ppm in pigmented plastics, while other grades and polymers may require substantially different levels.
This means that a dosage taken from another factory or another formulation cannot automatically be applied to your own product.
2. Start with the Plastic Material
The polymer is one of the first factors that affects dosage.
Common applications include:
PE
PP
PVC
PS
ABS
EVA
PET
PBT
PC
PA
PMMA
TPU
Different polymers have different transparency, natural color, polarity and processing temperatures.
The same optical brightener can therefore require different addition levels in different plastics.
For example, Archroma’s published application table shows different recommended concentrations for PET, PE/PP/PS, engineering plastics, PVC and EVA, even when the same optical brightener grade is used.
Therefore, dosage should always be discussed together with the polymer type.
3. Transparent and Pigmented Plastics May Require Different Dosages
The appearance of the plastic has a major influence on optical brightener efficiency.
Transparent Plastics
In transparent or highly translucent materials, relatively small amounts of optical brightener may already produce a noticeable fluorescent effect.
Too much emphasis should therefore not be placed on increasing dosage before lower levels have been tested.
Pigmented Plastics
White or pigmented plastics may contain:
Titanium dioxide
Fillers
Pigments
Other colorants
These materials can change how light passes through the polymer and how the fluorescent whitening effect is perceived.
As a result, pigmented plastics may require a different dosage range from transparent plastics.
Archroma’s technical guidance illustrates this difference, with significantly lower concentrations suggested for transparent plastics than for pigmented plastic systems in some applications.
4. The Optical Brightener Grade Also Matters
Not all optical brighteners have the same fluorescent efficiency, chemistry or compatibility.
For example:
Optical Brightener OB is widely used across many thermoplastic systems and provides broad compatibility.
Optical Brightener OB-1 is especially useful in polyester, polyamide and high-temperature engineering plastics because of its strong thermal stability.
Grades such as KCB and KSN also have different application ranges and fluorescent shades.
Therefore, changing from one optical brightener to another does not necessarily mean that the same dosage should be maintained.
The new grade should be retested in the actual formulation.
5. Initial Yellowness Affects the Required Dosage
The starting color of the resin is another important factor.
A clean virgin resin with only a slight yellow tone may require less optical brightener than a material with:
Strong natural yellowness
Recycled content
Previous thermal history
Color contamination
High filler loading
However, a strong yellow tone should not automatically be corrected by adding more optical brightener.
If the yellowing is caused by polymer degradation, excessive processing temperature or insufficient stabilization, the underlying cause should also be addressed.
Optical brighteners improve visual whiteness by absorbing ultraviolet light and emitting visible blue light, helping compensate for yellow tones; they do not reverse chemical degradation in the polymer.
6. Product Thickness Can Change the Visual Result
The thickness of the finished plastic should also be considered.
A thin film and a thick molded part may not show exactly the same whitening effect even when made from the same resin and formulation.
Examples include:
Plastic films
Sheets
Injection-molded parts
Extruded profiles
Foam products
Fibers
The amount of material through which light passes changes with product geometry and thickness.
For this reason, laboratory samples should ideally represent the actual finished product as closely as possible.
7. Other Additives Can Influence Optical Brightener Performance
An optical brightener does not work independently from the rest of the formulation.
Its apparent performance may be influenced by:
Titanium dioxide
Pigments
Fillers
UV absorbers
Antioxidants
Light stabilizers
Processing aids
Other colorants
This is particularly important when UV absorbers are present.
Optical brighteners depend on ultraviolet light to produce fluorescence, while UV absorbers are designed to absorb UV radiation.
The complete additive system should therefore be evaluated together rather than optimizing the optical brightener independently.
8. Dispersion Can Affect the Effective Dosage
A formulation may appear to require more optical brightener when the real problem is poor dispersion.
Because optical brighteners are used at relatively low concentrations, uniform distribution throughout the polymer is important.
Dispersion can be influenced by:
Particle size
Mixing efficiency
Feeding method
Processing temperature
Residence time
Masterbatch preparation
Compatibility with the resin
A well-dispersed optical brightener may provide a more consistent whitening effect than the same nominal dosage with poor distribution.
This is particularly relevant for high-melting products such as OB-1, where sufficient dispersion should be ensured in lower-temperature polymer systems.
9. More Optical Brightener Does Not Automatically Mean Better Performance
When a product is not white enough, the most common reaction is:
“Increase the dosage.”
But dosage should be optimized rather than increased automatically.
After a certain point, increasing the amount may not provide a proportional improvement in the finished product.
It will, however, increase formulation cost.
The better objective is:
Achieve the required whiteness and shade using the most appropriate effective dosage.
This requires testing rather than relying only on a theoretical number.
10. How Should You Determine the Right Dosage?
A controlled dosage trial is one of the most reliable methods.
Start with one suitable optical brightener grade and keep all other variables constant.
Use:
The same resin batch
The same pigment level
The same filler level
The same stabilizer system
The same processing temperature
The same processing time
Then prepare several samples with gradually increasing optical brightener concentrations.
For each sample, compare:
Whiteness
Yellowness
Final shade
Brightness
Dispersion
Surface appearance
Processing stability
The target is not simply the sample with the highest dosage.
The target is the lowest practical dosage that achieves the required appearance and performance.
11. What Does ppm Mean in Optical Brightener Dosage?
Optical brightener addition levels are often expressed in ppm, or parts per million.
For a mass-based formulation:
1 ppm = approximately 1 gram per metric ton of polymer.
For example:
100 ppm ≈ 100 g per metric ton
200 ppm ≈ 200 g per metric ton
This is why even a relatively small change in dosage can influence both whitening performance and formulation cost when production volumes are large.
However, published ppm values should always be treated as starting references rather than fixed requirements for every formulation.
12. Why Do Two Factories Use Different Dosages for the Same Product?
It is completely normal for two manufacturers to use different optical brightener dosages even when they appear to be producing similar plastic products.
Possible reasons include:
Different resin suppliers
Different resin grades
Different recycled-content levels
Different titanium dioxide levels
Different fillers
Different pigments
Different processing temperatures
Different optical brightener specifications
Different target white shades
Different product thicknesses
Therefore, asking:
“How much does another factory use?”
can provide a reference, but it cannot replace testing in your own formulation.
13. Should Optical Brightener Dosage Be Based on Price?
Price is important, but the cost of an optical brightener should not be evaluated only by price per kilogram.
A more useful comparison is:
Product price + required dosage + whitening performance + processing stability + final product quality
For example, if one optical brightener requires a lower effective dosage to achieve the target whiteness, its application cost may be competitive even if its price per kilogram is higher.
This is why manufacturers should compare cost in the final formulation, not only the purchase price of the additive.
A Practical Dosage Selection Process
A simple approach is:
Step 1 — Identify the Polymer
Confirm the resin and whether it is virgin, recycled or a blend.
Step 2 — Select a Suitable Optical Brightener
Choose the grade according to the polymer and processing temperature.
Step 3 — Check the Complete Formulation
Review pigments, fillers, TiO₂, UV absorbers and stabilizers.
Step 4 — Set a Starting Dosage Range
Use the supplier’s technical recommendation as the initial reference.
Step 5 — Prepare Several Trial Levels
Increase the dosage gradually while keeping all other conditions unchanged.
Step 6 — Compare the Finished Samples
Evaluate whiteness, yellowness, shade, dispersion and processing stability.
Step 7 — Calculate Application Cost
Determine which dosage achieves the required performance at the most economical formulation cost.
What Is the Best Optical Brightener Dosage?
There is no single number that can be recommended for every plastic.
The optimum dosage depends on:
Polymer + Optical Brightener Grade + Initial Color + Pigments + Additives + Processing Conditions + Product Thickness + Target Whiteness
Published dosage recommendations are useful starting points, but the final addition level should be confirmed through actual formulation testing.
Need Help Determining the Right Dosage?
If you are unsure how much optical brightener to use, tell us your polymer type, optical brightener grade, current dosage, processing temperature and target whiteness.
Blue Dolphin can help you evaluate suitable optical brightener options and optimize dosage according to your formulation and processing conditions.
Post time: Aug-12-2026