Foam Cannon Math, Solved: Bottle Mix vs Panel Impact Ratio (PIR)
Translate your target panel impact ratio into the exact bottle mix for any foam cannon draw ratio. Includes formulas, quick tables, and troubleshooting.
Why foam math feels messy
A foam cannon pulls solution from the bottle and cuts it further with rinse water. Two variables matter: the bottle mix and your cannon’s draw ratio (K). Together they determine the panel impact ratio (PIR) hitting paint. Our target could be 1:100, but that is only possible if the cannon draws enough soap.
Once you know K, you can work backwards. The MixByParts formula translates your preferred PIR into a bottle mix strength that survives the additional water your cannon injects. No more guessing “fill to the first line and hope.”
Foam cannon calculator presets
Prefer to click instead of crunch? Start from these 1 L detailing presets and tweak draw ratio or density inside the mixer:
Working on rinseless buckets too? Pair this with the 1:256 rinseless guide so every prep bucket and foam pre-wash share a consistent playbook.
The only formula you need
Let K represent the draw ratio (parts of extra water added per 1 part pulled from the bottle). Let R represent the desired PIR water:product ratio — so R = 100 for a 1:100 target. The required fraction of product in the bottle is:
f = (1 + K) ÷ (R + 1)
Once you have f, convert it into a bottle ratio: product : water = f :1 − f. For 1 L bottles, product mL =f × 1000. That is it.
Stop guessing the dial
If your cannon needs more than ~160 mL of concentrate for decent foam, the draw ratio is weak. Check the dial, swap the orifice, clean the mesh screen, or accept that you are chasing Instagram foam instead of PIR precision.
Quick examples (K = 10)
- Target 1:100 → f = 11 ÷ 101 ≈ 10.9% → ~109 mL product in a 1 L bottle (about a 1:8.2 bottle mix).
- Target 1:150 → f ≈ 7.28% → ~73 mL product in 1 L.
- Target 1:200 → f ≈ 5.47% → ~55 mL product in 1 L.
Translate any other combination by plugging K and R into the same formula. The 1:100 in 1 L calculator is a fast baseline — switch to weight mode if you have soap density handy (for example, 109 mL × 1.05 g/mL ≈ 114 g).
1 L quick table (mL of product)
| Draw K | 1:80 | 1:100 | 1:150 | 1:200 |
|---|---|---|---|---|
| 6 | 86 mL | 69 mL | 46 mL | 35 mL |
| 10 | 136 mL | 109 mL | 73 mL | 55 mL |
| 15 | 198 mL | 158 mL | 106 mL | 80 mL |
| 20 | 259 mL | 208 mL | 139 mL | 104 mL |
Numbers above assume a 1 L bottle. Scale them by the actual bottle size if yours differs. For instance, at K = 10 and a 32 oz bottle (946 mL), product = 0.109 × 946 ≈ 103 mL.
How to measure your draw ratio (K)
Quick stopwatch + measuring cup
- Fill the cannon bottle with exactly 1 L of water.
- Spray into a bucket for 10 seconds.
- Measure how much solution left the bottle (bottle draw) and how much landed in the bucket (total output).
- Compute
K ≈ (total − bottle) ÷ bottle.
Better: weigh it
- Weigh the filled bottle. Spray for 10 seconds and weigh again to get bottle draw in grams (≈ mL).
- Collect and weigh the foam output for the same interval.
- Use the same formula above to solve for K. Warmer water often improves consistency.
Density tweaks? Multiply any table value by your soap density to weigh viscous soaps: grams = mL × density. For example, 109 mL at 1.05 g/mL ≈ 114 g concentrate.
FAQs
Do I need a precise PIR?
Not really. Foam’s job is lubrication and dwell. Stay in a repeatable range (1:80–1:150) that your soap and cannon can deliver, then focus on contact wash technique.
Why does my foam look thin?
Weak draw is the usual suspect. Clean the injector, confirm pump pressure, warm up the water, and double-check K using the methods above.
Can I use rinseless ratios for foam?
Rinseless panel ratios (like 1:256) are much lighter. If you want that math, mix the rinseless bucket separately and use this guide for the pre-wash foam step.
Dial in every wash step
Save the links below so your crew can jump straight into calculator presets and companion guides.