Watercolor Pans vs Tubes: The Real Difference (Explained by a Paint Factory)
Watercolor tubes contain moist paint holding roughly 38–42% pigment by weight and stay usable for 6–18 months after opening. Pans are dry cakes at 55–60% pigment load that stay usable for 8–10 years with normal storage. Tubes win volume and fast mixing; pans win portability, shelf life, and cost per usable stroke. Most working watercolorists keep both.
A watercolor tube is pigment suspended in a soft paste — gum arabic (binder) plus a humectant like honey or glycerin that keeps the paste moist for shelf life. A watercolor pan is pigment bound in a dried cake of gum arabic with minimal humectant. Same pigments, same binder family, different water content. Everything else flows from that.
The Real Difference: It Is Binder Chemistry, Not Just "Wet vs Dry"
Most guides stop at "tubes are wet, pans are dry." That is true, but it is the observation, not the cause. What actually drives every downstream behavior — mixing speed, saturation, shelf life, cost per ml — is the humectant ratio in the binder. Tubes need humectants because paste would crack and separate on the shelf. Pans do not: a dried cake that never needed honey stays stable for years because there is almost nothing in it that can biologically or chemically fail.
This chemistry is why the two formats behave differently even when the pigment inside is identical. Paul Rubens runs the same pigment batch through both product lines; the finished pan and the finished tube will mix, lift, and stain slightly differently because the binder composition is not the same. Schmincke, one of the oldest watercolor houses in Germany, notes that pan and tube formulas are not interchangeable and are adjusted separately for each pigment (Schmincke FAQ).
Head-to-Head: 10 Criteria That Actually Matter
Forget the vague "studio vs travel" summaries. Below are the ten dimensions that decide which format suits your work, with factory numbers where we have them.
| Criterion | Pans | Tubes |
|---|---|---|
| Binder chemistry | Gum arabic + minimal humectant, dried | Gum arabic + honey or glycerin, paste |
| Pigment load (% by weight) | 55–60% | 38–42% |
| Shelf life after opening | 8–10 years (dry storage) | 6–18 months (cap sealed) |
| Portability | Excellent — built-in palette, no leaks | Limited — tubes can split on planes or in hot cars |
| Large-wash volume | Requires repeated re-wetting | Ideal — squeeze once, mix a puddle |
| Mixing speed | Slower — paint must rehydrate first | Faster — paint is already wet |
| Cleanup | Almost none — wipe the palette | More mess — tube caps, palette wells, squeezed excess |
| Price per ml (like-for-like grade) | Higher upfront; lower per usable stroke | Lower upfront; higher waste risk |
| Learning curve | Forgiving — small amounts, less waste | Easy to over-squeeze as a beginner |
| Re-wetting behavior | Clean — full pigment recovers after 30–60 s soak | N/A — always wet in the tube |
Shelf Life: What the Factory Data Actually Shows
If you have ever wondered why a pan set you forgot in a drawer is still perfectly usable while a half-squeezed tube has gone crusty, this is the most under-discussed difference between the two formats. In controlled storage at 20 °C and 45% relative humidity, Paul Rubens artist-grade tubes retain full working consistency for 6 months after opening; below that, you are fighting a stiff paste that cracks under the brush. Pans under the same conditions stay indistinguishable from new for 8 to 10 years — we have retail pan sets from 2015 still performing in the lab.
Dick Blick, the US art-supply retailer, publishes similar guidance: they quote pans as "virtually indefinite" shelf life and tubes as "up to several years unopened, significantly less once opened" in their reference specs (Dick Blick product pages). The gap is that large because once a tube is unsealed, evaporation and microbial growth start work on the humectant — neither happens to a dried pan.
Practical takeaway: if you paint less than weekly, pans waste less money. If you paint almost daily in volume, tubes can be the cheaper option because you use them up before they deteriorate.
Pigment Concentration: Why Pans Often Feel More Saturated
The second factory insight that rarely makes it into blog comparisons: pigment concentration. Our QC line measures pigment-to-binder ratio for every batch. Artist-grade watercolor tubes come off the fill line at 38–42% pigment by weight — the rest is gum arabic, humectant, dispersant, and water. The same pigment pressed into a half-pan and dried sits at 55–60% by weight, because the pan has lost most of its water and all of its humectant during drying.
Per milliliter of dry product, a pan holds meaningfully more pigment than a tube. The usage math is messier — a tube squeeze releases more paint per second than a wet brush can lift from a pan — but when you match volumes carefully, a pan mix can look a half-stop more saturated on the same paper.
That saturation difference is the honest reason many experienced painters keep a pan set on the desk even when their main studio supply is tubes. Our guide on watercolor paper weight covers the other half of saturation — how absorbency and sizing affect what that extra pigment actually does on the page.
Use-Case Matrix: Which Format Wins When You…
No format wins every scenario. Here is the honest breakdown we see in customer behavior data across five common use cases.
| Scenario | Winner | Why |
|---|---|---|
| Plein-air sketching & travel | Pans | No caps, no leaks, built-in palette. The whole kit weighs under 300 g. |
| Large-format studio washes (A3 and up) | Tubes | Squeeze a puddle once; mix a liter of wash in 30 seconds. |
| Illustration / hobbyist practice (A4 and smaller) | Pans | Less waste, no cap-opening friction, faster setup. |
| Classroom or shared workshop | Pans | Nothing to squeeze, nothing to cross-contaminate tubes. |
| Highly saturated commissioned work | Tubes | Mix fresh, never fight re-wetting, match colors across sessions. |
How to Convert Tube Paint Into Pan Paint (Step by Step)
A surprising number of painters switch to the hybrid workflow once they realize they can decant tube paint into empty pans. This saves money if you already own tubes, lets you travel with tube-grade saturation, and gives you full control over palette layout. The process is simple, but there are three common mistakes that ruin a batch.
- Prep the pan. Use an empty full-pan or half-pan. Wipe clean and set on a flat surface; tilting during fill causes a sloped dry surface that lifts unevenly later.
- Squeeze slowly. Fill the pan in thin layers — about one-third full at a time. A single deep squeeze traps air pockets that crack as the paint dries.
- Spread with a palette knife or toothpick. Push the paste into the corners and surface the top. A flat fill dries faster and re-wets cleaner than a domed fill.
- Cure open for 48–72 hours. Leave the pan uncovered in a dry room (below 55% relative humidity). Shorter cures leave soft paste underneath a dry skin.
- Refill once shrinkage appears. Tube paint loses roughly 20–25% of its volume as it dries. Top up with a second thin squeeze after the first cure, then let it dry for another 24 hours.
Common mistakes to avoid:
- Curing in a humid room. Above 60% relative humidity, gum arabic does not harden properly and you end up with a sticky half-cake that lifts under the brush.
- Filling in one thick layer. Air pockets form under the skin and the cake cracks. Thin layers cure evenly.
- Mixing pigments in the same pan. Even two colors from the same brand can separate if their binder ratios differ. One pan, one pigment.
The Hybrid Workflow (What Most Working Watercolorists Actually Do)
Ask a gallery-level watercolorist which format they prefer and nine times out of ten the answer is "both." Studio sessions use tubes for volume and fresh mixing; travel, plein-air, and quick sketches use a pan palette that lives in a bag. The two formats are not competing products — they solve different problems in the same practice.
A workable hybrid kit for most painters looks like this: a 24-color artist-grade pan set as the base travel and illustration kit, a matching 24-color tube set for studio washes, and an empty palette with refillable half-pans so you can decant tubes when you want tube saturation in a portable format. This covers roughly 95% of what most artists ask their watercolor kit to do.
What the Label Actually Tells You (Pan or Tube)
Before choosing between pan and tube, the bigger decision is whether you are buying artist-grade or student-grade paint. Format matters less than grade — a premium tube and a premium pan from the same factory behave more like each other than a student-grade pan does to an artist-grade pan. Here is what to look for on the label of either format, regardless of brand.
Pigment code (PB29, PR108, PY35). Every serious watercolor, pan or tube, prints the pigment codes on the tube barrel or pan wrapper. A single-pigment color with one code (for example "PB29" for ultramarine blue) is cleaner in mixes than a multi-pigment hue that blends two or three codes to approximate a named color. Student-grade paints often hide this by printing only a marketing name.
Lightfastness rating (LF I / LF II or the ASTM grade). This tells you how many years the dried paint holds its color under normal indoor light. LF I (ASTM I) means archival — a hundred years without visible fading. LF III and below will shift within a decade on a sunlit wall. Tubes and pans use the same rating system; the number does not change with format.
Series number (1 to 5 or "S1" to "S5"). Series indicates pigment cost, not quality. A Series 1 color uses inexpensive pigments such as earth tones or some organic blues; a Series 5 uses expensive ones like genuine cobalt, cadmium, or quinacridone. Both can be artist-grade. Paul Rubens standardizes pigment load across series so saturation stays consistent while the raw material cost varies.
Transparency symbol (solid square, half-filled square, hollow square). This is printed on both pans and tubes. A solid square means opaque; hollow means fully transparent; half-filled is semi-transparent. It matters more than many beginners realize: transparent colors are what let watercolor glow, opaque colors are what save a passage when you need to correct it.
Factory takeaway: the same label vocabulary applies to both formats, so learn to read one label and you can judge quality in any aisle. Format is the comfort decision; grade is the quality decision. Pick the grade first, then pick the format.
Product Recommendations (Three Honest Options)
Below are the three Paul Rubens watercolor sets we recommend for the three most common situations. These are the same pigments our studio uses; pricing reflects direct-from-factory positioning so you get artist-grade behavior at a mid-tier cost.
Paul Rubens 24-Color Solid Watercolor Pan Set
Twenty-four artist-grade half-pans in a portable metal case with a built-in mixing palette. Pigment load sits at the 55–60% range discussed above, which is why re-wetting recovers full saturation in 30–60 seconds.
- 24 lightfast pigments in removable half-pans
- Metal case with hinged mixing palette
- Fits in a sketchbook pocket (under 300 g)
- Best for plein air, travel, illustration, classroom
Paul Rubens 24-Color Traditional Watercolor Tube Set
Twenty-four 5 ml tubes formulated for transparency and fluidity — the same pigment family as the pan set but in a paste designed for fast mixing of larger washes.
- 24 transparent artist-grade colors in 5 ml tubes
- Paste optimized for smooth large washes
- Ideal for studio work, A3+ formats, commissions
- Pairs with any watercolor palette
Paul Rubens 52-Color Travel Watercolor Set + Paper
Fifty-two half-pans plus Paul Rubens 140 lb / 300 gsm 50% cotton hot-pressed organ-style paper in one bundle. Purpose-built for plein-air sessions where you want pan portability and real cotton paper in one kit.
- 52 colors in a compact travel case
- Paired with 14 sheets of 140 lb / 300 gsm cotton paper
- Hot-pressed finish for detail work on the road
- Best for plein air, outdoor workshops, travel journaling
If you are still deciding whether to start with watercolor or acrylic, our companion guide on getting started with acrylics covers the other half of the "first-medium" question — different trade-offs, different learning curves.
Common Mistakes Painters Make With Both Formats
- Buying only tubes as a beginner. First-time painters tend to over-squeeze. An entire 5 ml tube of cadmium red can end up on a palette in week one; most of it dries before use.
- Buying only pans if you paint large. Wetting a pan enough to flood an A3 wash takes longer than mixing a tube puddle. The technique is different; large-format plein-air painters often still carry a couple of tubes.
- Storing tubes standing up on the cap. Pigment settles against the cap; the first squeeze after storage dumps clear binder onto the palette. Store tubes cap-up, label-out.
- Letting a pan set go damp. Damp pans grow mildew on the gum arabic and the pans swell and pop out of the tray. Always air-dry before closing the lid.
FAQ
Are watercolor tubes or pans better for watercolor?
Neither is universally better. Tubes are better for large studio washes, fast mixing, and highly saturated commissioned work. Pans are better for travel, plein-air, classroom use, shelf life, and beginners learning to meter paint. Most working watercolorists keep both formats.
What are three common mistakes people make when using watercolor?
First, over-squeezing tubes — a beginner typically wastes 60–70% of their first tube. Second, using too little water with pans — dried pans need a 30–60 second soak to release full pigment. Third, buying student-grade paint in either format and assuming it behaves like artist-grade; the pigment load is the variable, not the container.
Can you turn watercolor tubes into pans?
Yes. Squeeze tube paint into empty half-pans in thin layers, spread flat with a palette knife, and cure uncovered for 48–72 hours in a dry room. Refill once after shrinkage. The five-step process is detailed earlier in this guide.
Why are watercolor tubes cheaper per ml?
Tubes are not always cheaper per ml — they are often cheaper at purchase price because each tube contains proportionally more water, humectant, and binder and less pigment. When you normalize for pigment load, pans are typically the more concentrated product per dollar.
Do watercolor pans expire?
In normal dry storage, artist-grade pans stay usable for 8 to 10 years with no visible change in performance. Pans only fail when stored damp — mildew growth on the gum arabic binder ruins the cake.
Can I take watercolor pans or tubes on a plane?
US TSA permits both in carry-on and checked bags. Pan sets travel better because they cannot leak. Tubes can split from pressure changes in checked luggage; if you fly with tubes, pack them in a sealed plastic bag in your carry-on.
TL;DR — Pans vs Tubes in 8 Bullets
- Same pigments, different binders: pans are dry, tubes are paste with honey or glycerin.
- Pans carry more pigment per gram (55–60% vs 38–42% for tubes).
- Pans last 8–10 years in storage; tubes last 6–18 months after opening.
- Tubes win large washes and fast mixing. Pans win portability and shelf life.
- A dried pan re-wets to full saturation in 30–60 seconds.
- You can convert tube paint to pan paint in five steps over three days.
- Most working watercolorists use both formats for different jobs.
- Start with pans if you are a beginner; add tubes when you begin painting larger than A4.
Ready to choose your first real watercolor set?
Paul Rubens makes both pans and tubes from the same artist-grade pigment line. Start with the pan set for portability, or the tube set for studio volume — or skip the decision and get the 52-color travel bundle with paper.
Shop all Paul Rubens watercolors →