Airbrush Flow Improver vs Thinner: A Paint-Family Comparison
A thinner is typically made to reduce how thick the paint is so it atomizes, and a flow improver is typically made to improve flow-out and leveling and to delay drying — including at the nozzle and tip. They are different jobs, and the exact formulations and roles are set by the instructions for that product line.
They sit next to each other on the shelf and they are not the same product. The table below separates their typical jobs. The second table separates your paint by family — water-based acrylic, alcohol-based acrylic, and lacquer or other solvent-based — because the instructions for that chemistry, and for that exact line, decide what belongs in the cup.
The short answer
Four lines cover most of it.
- Different jobs, not two strengths of the same product. A thinner typically reduces the paint's thickness so it atomizes. A flow improver typically improves flow-out and leveling and can delay drying at the surface and at the nozzle.
- Name the cause before the product. Tip dry is a symptom with more than one possible cause — paint mixed too thick, a fast-drying paint, airflow and pressure, humidity, a dirty or damaged needle, or a product your paint instructions do not cover. A thinner answers one of those. A flow aid is one possible answer and not a universal one.
- Your paint family sets the shortlist. Water-based acrylics, alcohol-based acrylics and lacquer systems are different chemistries, and each maker's own range names the products that belong to that line.
- The label outranks this page. Formulations differ between makers and change over time. Where a general comparison and your paint maker's instructions disagree, the maker's instructions win.
Thinner vs flow improver: what each one is for
Read down the left column, then across to the product that answers it.
| The question | Thinner (reducer) | Flow improver |
|---|---|---|
| What it is made to change | The paint's thickness (dilution) — how readily it atomizes through the nozzle. | Flow-out, leveling, and how long the paint stays workable — including delayed drying at the nozzle and tip. |
| Reach for it when | The mix is genuinely thicker than the nozzle and pressure you are spraying at call for — and your paint maker names a thinner for that exact line. | The mix is at the thickness your instructions call for and the pass still shows tip dry or poor flow-out, and the product's instructions permit a flow aid or retarder for that line. Tip dry has several causes, so check the others too. |
| It will not fix | A needle that is already dirty or damaged, a blocked nozzle, air that is very dry or very humid, or a product in the cup that your paint instructions do not cover — and it is the wrong first move if the mix is already at the thickness your instructions call for. | A mix that is genuinely too thick for the setup in your hand — that is a thinning job. It is not a substitute for the thinner the maker names for the line. |
| Where it sits in your order of work | First — and only when the mix itself is the cause you have actually confirmed. | Alongside thinning or after it — a small addition once the mix, needle and conditions are checked, and only if the product's instructions permit it. |
| What decides the exact product | The paint maker's instructions for your exact paint line. | The paint maker's instructions for your exact paint line. |
This table describes typical jobs. Formulations and directions vary by product; the label and the maker's instructions decide what to use and how much.
A published example of both together. Vallejo’s Model Color basic use guide for airbrushing mixes Field Blue 70.964 with Airbrush Thinner 71.261 at two parts thinner to two parts paint (1:1), then adds Flow Improver 71.262 at three drops per ten drops of paint and stirs thoroughly. That is one maker’s worked example for one named line — not a ratio for Model Air or another brand.
Model Air is a different line. Vallejo’s 2026 Model Air chart lists 71.261 Airbrush Thinner for dilution and 71.262 Flow Improver for delaying drying. Keep the Model Color 1:1 example with Model Color; do not carry it across to Model Air.
Tip dry: more than one cause
Tip dry is a symptom, not a diagnosis. Paint drying on the needle and nozzle can come from several different causes, and which product — if any — answers it depends on which cause you actually have. A flow improver is one possible answer, not the default one, and not every paint line calls for one.
Possible causes, in no particular order:
- Paint mixed too thick. A mix the nozzle and pressure cannot atomize cleanly can build up and set at the tip. This one is a thickness problem, and thickness is what a thinner is for.
- A fast-drying paint. Some chemistries — alcohol-based acrylics and lacquers in particular — set at the tip faster than others by design.
- Airflow and pressure. Too much air, too little air, or a nozzle, needle and cap combination that does not match the job all change how long paint sits at the tip.
- Humidity and ambient conditions. Dry air and warm air pull solvent out of the paint faster; humid air can leave it behaving differently again. A mix that worked in one room may not behave the same in another.
- A dirty or damaged needle and nozzle. Dried paint on the needle, a bent tip or a partly blocked nozzle produces the same symptom as a paint problem. Clean and inspect before you change the mix.
- Incompatible products in the cup. If something in the mix is not covered by your paint maker's instructions for that line, the result is not predictable — and the fix is to stop combining them, not to add a third product.
Work through those before you open an additive; a flow aid can help with tip dry in some lines, but it is not the default. If the mix is genuinely too thick for your setup, thin it with the thinner your paint maker names for that exact line, and only for that reason. If the mix is already at the thickness the instructions call for and the pass still misbehaves, a flow aid or retarder is worth considering only where the product's own instructions permit one.
By paint family: who decides what goes in the cup
Find your paint's family, then read who has the final word.
| Paint family | What you are looking for in that family's own range | Who decides for your bottle |
|---|---|---|
| Water-based acrylic | The maker's own line for that paint, and whether the maker names a thinner and a flow improver as separate products for it. | The label and the product information your paint maker publishes for that exact line. |
| Alcohol-based acrylic | The maker's own thinner for that line, and whether the maker names a flow improver or a retarder for it at all. | The label and the product information your paint maker publishes for that exact line. A water-based additive is not covered by those instructions. |
| Lacquer and other solvent-based paints | The maker's thinner for that system, and how the maker says the system is handled. | The label, your paint maker's product information, and your airbrush manual for what the brush is rated to handle. |
| A line where the maker names only one product | What the maker says that single product is for, and nothing beyond it. | The maker. If the label does not cover what you are doing, ask them rather than borrowing another family's answer. |
The products are listed by family because chemistries differ. This table does not say any maker's product works in another maker's paint, and it does not replace the instructions that came with yours.
Pairings to avoid
Each of these is avoidable, and none of them needs a new airbrush.
1. A thinner from a different paint family.
A thinner is made for the chemistry it was sold for. If your label does not name it, it is not covered by your label.
2. Flow improver instead of the named thinner for a mix that is too thick.
That is a thinning job. Use the thinner the maker names, and keep the flow improver for the job its instructions give it.
3. Reaching for an additive before you know why the tip dried.
Tip dry can come from paint mixed too thick, a fast-drying paint, your airflow and pressure, the humidity, a dirty or damaged needle, or products your paint instructions do not cover. Identify the cause first; the product follows the cause, not the other way round.
4. One ratio copied across your paint lines.
Different families, different makers and different lines each carry their own instructions. A number that worked once is not a setting.
5. Pre-mixing an additive into the bottle.
Add to the cup, not the bottle. You can still change a cup; you cannot undo a bottle.
6. Treating thinner, flow improver and retarder as one product.
They are sold as separate products because they are made for separate jobs. Check what your maker names each one for.
Choosing for the bottle in front of you
Six steps, in order. Do not skip to a number.
Read the label on your bottle.
Find what your paint maker says about thinning and about additives for that exact product line. If the label does not cover what you are doing, stop there and check the maker's own published information.
Name the paint family.
Water-based acrylic, alcohol-based acrylic, or lacquer and other solvent-based. The family tells you which of the maker's own products are even in scope.
Name the cause you actually have.
Too thick to atomize is a thinning job — and only when the mix really is too thick. Tip dry on its own is not automatically a flow job: it can be the mix, the paint's drying speed, your airflow and pressure, the humidity, a dirty or damaged needle, or a product your instructions do not cover. Decide before you open anything.
Use the product the maker names for that job, if they name one.
Not the one that is closest on the shelf, and not one borrowed from another paint line. If your paint's instructions do not permit a flow aid or retarder for that line, do not add one — go back to the cause list.
Test on scrap, one change at a time.
Same pressure, same distance, same surface as the model. Change the mix or the additive, then retest — never both at once.
Write down what you used.
Paint, product, how much, pressure, nozzle and needle size, and what the pass did. A result you cannot repeat is not a result.
Where this comparison stops
Four things this page leaves to the product instructions.
1. Your exact dose.
A published example such as Vallejo’s is a starting point for that line, not a universal amount. The amount moves with the product line, the nozzle and needle size, the pressure and the paint's condition; the product's own instructions are the authority.
2. A compatibility verdict.
This page does not rule on whether any named manufacturer's product works in another manufacturer's paint. That answer belongs to the two labels in front of you.
3. A substitute.
They are different products. Follow the maker's instructions rather than swapping one for the other on assumption, and check both labels before combining anything.
4. A permanent answer.
Formulations change, and packaging gets revised. A comparison written once cannot track that. The instructions that came with your bottle can.
Handling and safety
Solvent-based and alcohol-based products are not handled the same way as water-based ones.
- Spray in a well-ventilated area, and follow the safety information on the labels of the paint and of every product you add to it, including any respiratory protection those labels call for.
- Keep solvent-based thinners and additives away from open flames, pilot lights and other ignition sources, and away from children and pets.
- Check your airbrush manual for what your brush is rated to handle before you spray a solvent-based product through it. The manual governs your brush, not this page.
- If your label does not cover a product you want to use, or a product has changed color, smell or texture, do not spray it. Check the paint maker's own information first.
FAQ
Is flow improver the same as thinner?
No. They are made for different jobs. A thinner is typically made to reduce paint thickness so it atomizes. A flow improver is typically made to improve flow-out and leveling and to delay drying — including at the nozzle and tip. Exact formulations and directions come from the product's own instructions.
Is tip dry always a flow improver problem?
No. Tip dry is a symptom with several possible causes — paint mixed too thick, a fast-drying paint, your airflow and pressure settings, the humidity and ambient conditions, dried paint or damage on the needle and nozzle, or a product in the cup that your paint instructions do not cover. A thinner is the answer when the mix is genuinely too thick, and only a thinner your paint maker names for that line. A flow aid or retarder is worth considering only where the paint's own instructions permit one. Not every line calls for one, and flow improver is not a universal requirement.
Can I use the same thinner for my water-based acrylics, my alcohol-based acrylics and my lacquers?
Treat those as three different chemistries with three different sets of instructions. Each maker's own range names the products that belong to that line, and a thinner sold for one family is not covered by another family's instructions. Read the label on the paint, read the label on the product, and if your paint maker does not name it, check their published information before you combine anything.
How much flow improver should I add?
Vallejo’s Model Color airbrushing guide gives three drops of Flow Improver 71.262 for every ten drops of paint in its Field Blue 70.964 example. That is one maker's published example for one line; check your own product's instructions for whether to add one and how much. Start from that, change one thing at a time, and judge the result on scrap.