What Is Blending? A Beginner's Lesson on Blending Car Paint
Introduction
"Can you make it match?" Almost every customer asks me that. The honest answer is that new paint never matches old paint 100 percent. What a good painter does is make the difference impossible to see. That skill is called blending.
I am KJ Lee from Ace Auto Body Inc. in Hackensack, NJ, and I have been painting cars for about 20 years. In Basic Car Paint Guide for Beginners, blending was one short section. In this lesson we go deeper. We answer six questions:
- What is blending, and why can't new paint just match?
- When do we blend, and when do we paint the whole panel?
- Where should the blend end?
- How do we prepare a panel for blending?
- How do we spray a blend?
- What happens with the clear coat over a blend?
Key Takeaways
- Blending hides a small color difference. It does not fix a wrong color. The color must be close first.
- Plan the blend before the repair starts, and decide which panels will be blended.
- On the side of a car, end the blend around the middle of the next panel. Special colors need more room.
- Scuff every area that will get color or clear. Clear over an unscuffed area can peel later.
- Use as little color as possible on the blend panel, and spread it with an X pattern.
- The clear must cover all of the color. Most paint systems want the whole panel cleared.
Blending at a glance.
Learning Objectives
By the end of this lesson, you will be able to:
- Explain what blending is and why it is needed.
- Decide where a blend should start and end on a car.
- List the prep steps for a blend panel.
- Compare three blending methods: standard, reverse, and wet-bed.
- Describe the X pattern and a 75 percent overlap.
- Explain how clear coat is applied over a blend.
Before You Start
- What you should already know: the paint layers (sealer, base coat, color coat, clear coat). If these are new, read Basic Car Paint Guide for Beginners first.
- How to use this lesson: each section ends with a Check Yourself question. Answer it before you move on. The answers are in the Review Questions near the end.
- Time to read: about 12 minutes.
One rule before we start: every paint system has its own written blending procedure and technical data sheet (TDS). The numbers here come from trade sources and our shop. When your paint maker's instructions say something different, follow your paint maker.
1. What Is Blending, and Why Can't New Paint Just Match?
Blending means spraying new color so it fades into the old paint over a wide area, instead of stopping at a sharp edge.
Figure 1. A hard edge shows the difference; a blend hides it.
Why can't the new paint match exactly? There are many small reasons, and they add up:
- The old paint has aged. Years of sun change it a little.
- Factory colors vary. The same paint code can come out slightly different from one plant or year to another.
- The mix can be a little off. Over- or under-pouring a toner, the wrong reducer, or the wrong formula all change the color.
- The painter's technique changes the color, especially with metallic and pearl paints. Gun setup, distance, and speed all matter.
A trade article on blending puts the goal simply: if the match is slightly less than perfect, the eye is tricked into not seeing the subtle change. That is all blending does. It does not turn a wrong color into a right one. The color must already be close, and that is why we check it on a spray-out card first.
Does blending fix a color that is clearly wrong?
2. When Do We Blend, and When Do We Paint the Whole Panel?
In real repair work, nearly every job needs some blending. Experienced painters decide which panels will be blended before the repair starts, not after the color looks wrong.
We blend when:
- the repaired panel sits next to an undamaged panel (for example a new front door next to an old rear door),
- the color is metallic, pearl, or tri-coat, because these colors change with the viewing angle and are the hardest to match,
- the color is one we know is difficult, or the spray-out card is close but not perfect.
We may skip blending when a solid color (no metallic or pearl) matches perfectly on the card, and the repaired part is separated from the next panel by trim or a large gap. Even then, the card decides, not the paint code.
Blending is not "half a paint job." A trade article on blend time points out that blending most of today's metallic colors takes more preparation and skill than painting a whole panel, and it uses almost as much clear coat. Customers sometimes ask why the estimate includes a panel that was not damaged. This is the reason.
Name two kinds of color that almost always need blending.
3. Where Should the Blend End?
The blend needs enough room for the color to fade out. If the room is too short, the fade is too fast and the eye can still find it.
Figure 2. Where the blend ends on the side of a car.
Guidelines from the trade sources:
- Side panels: blend to about the center of the next panel.
- Hood and trunk lid: blend over a crown (a curved high point) in the next panel. Light reflects differently over a crown, which helps hide the change.
- Minimum room: PPG's blending procedure calls for at least 12 inches from the panel edge for factory, translucent, and special-effect colors, and at least 24 inches for tri-coat and quad-coat colors.
- Where the eye won't look: end the blend at an angle, not in a straight vertical line, and where shadows fall naturally, such as under a mirror.
A good blend at the base coat stage looks like this: the color is strongest over the repair and fades out softly, with no line.
On a hood, where is a good place for the blend to end?
4. How Do We Prepare a Panel for Blending?
A blend panel is an undamaged panel, so beginners think it needs no prep. It needs careful prep, because new paint and clear must stick to old paint.
- Clean the panel with a wax and grease remover (we use PREP-ALL).
- Scuff every area that will receive color or clear. We use a gray scuff pad with scuff paste, or wet sand with fine paper. In our shop that is P1000 or P1500 on the old paint, as shown in Part 4. One trade article recommends P1500 or finer, or scuff pads, following your paint maker. If a panel is not scuffed properly, the paint can peel (delaminate) later.
- Wipe off all the scuff paste. Left-over paste shows up as marks in the paint.
- Mask the blend panel while you seal the repair panel, then unmask it before you blend. Sealer overspray on the blend panel leaves rough, dry spray.
- Clean the dust: static cloth after PREP-ALL, and tack cloth before painting starts.
What can happen if the blend area is not scuffed?
5. How Do We Spray a Blend?
5.1 Plan the Spray Direction
Before picking up the gun, plan the passes: which way the gun will move and where the blend will end. A plan keeps the passes even.
5.2 Three Ways to Build a Blend
Figure 3. Three ways to build a blend.
| Method | How it works | Good for |
|---|---|---|
| Standard | Each coat goes a little farther than the last. The first coat goes about 4 to 6 inches into the old paint. | Most colors |
| Reverse | The first coat goes farthest (about 12 to 14 inches), then each coat is shorter. | Metallics such as silver, gold, and bronze |
| Wet-bed | A wet clear "bed" coat goes on first, then color is applied in the reverse pattern. | Colors with a history of trouble |
Another trade source describes the standard method as extending each coat about 2 to 3 inches farther than the one before. The exact distance changes with the color and the panel. What does not change is the idea: the color thins out gradually.
5.3 The X Pattern and Overlap
Figure 4. The X pattern, overlap, and gun technique.
In our shop we blend in an X pattern: one pass goes diagonally one way, and the next crosses it. Crossing passes spread the color evenly and help the new color settle into the old one. This is a hand skill, and it takes years to learn.
Technique tips from the trade sources:
- Overlap about 75 percent. Paint makers now suggest 75 percent rather than the older 50 percent.
- Keep the gun square to the panel, and let off the trigger at the end of each pass. Flicking or fanning the gun can leave a halo and can disturb metallic flakes. PPG describes a slight arcing motion and warns against wrist flicking.
- Use as little color as possible on the blend panel. If you dust color over the whole panel, you did not blend it.
- Use a slower reducer when it is hot. A fast-drying reducer can make the blend edge look coarse.
- Give the color time to flash before the next coat or before clear. Follow the TDS; more coats need more time.
What is the difference between the standard and reverse blending methods?
6. What Happens With the Clear Coat Over a Blend?
The color is only half of the blend. The clear coat must cover all of the color, because base and color coats have no protection of their own.
Figure 5. The clear goes past the end of the color.
- Most paint systems want the whole panel cleared, to the panel edge. This is the safest choice, and it is how we work.
- Only put clear on scuffed areas. Clear over an unscuffed area can peel.
- If a clear blend is used, trade sources say to taper each clear coat a little past the last one, and to use blending solvent sparingly, because too much makes the clear sag at the edge. The edge is then wet sanded and polished after it dries. Clear blending is not recommended on horizontal panels like hoods and roofs, where the sun can make the edge fail.
- Tack off before clear. One trade article recommends a tack cloth made for base coat, which is less sticky, so it does not disturb metallic flakes.
- On the blend panel, our habit is to let the paint dry completely first and check its condition before spraying, because the way it dries changes how glossy it looks.
Why should clear never go on an area that was not scuffed?
Common Misconceptions
| What people think | What is true |
|---|---|
| "Blending fixes a wrong color." | Blending only hides a small difference. The color must be close first. |
| "The blend panel was not damaged, so it needs no prep." | It must be cleaned and scuffed, or the new paint can peel. |
| "More color on the blend panel gives a better match." | Less is better. Heavy color on the blend panel defeats the blend. |
| "A short blend is fine if the color is good." | Special colors need room: at least 12 in., and 24 in. for tri-coats (PPG). |
| "Blending is half the work of painting a panel." | Most metallic blends take as much prep and skill as a full panel, and almost as much clear. |
| "End the blend in a straight line along a body line." | A straight vertical end is easier to see. Angle it and end where shadows fall. |
Try It Yourself: Practice a Blend on a Scrap Panel
Quick Review
Frequently Asked Questions (FAQ)
Glossary
Review Questions (with Answers)
1Does blending fix a clearly wrong color?SHOW ANSWER ▾
2Two kinds of color that almost always need blending?SHOW ANSWER ▾
3Where should a blend on a hood end?SHOW ANSWER ▾
4What happens if the blend area is not scuffed?SHOW ANSWER ▾
5Standard vs. reverse blending?SHOW ANSWER ▾
6Why no clear on an unscuffed area?SHOW ANSWER ▾
Shop Tips
- ✓Decide the blend panels before the repair, not after the color looks off.
- ✓Spray the card first. Blending hides small differences, not big ones.
- ✓Less color on the blend panel. Let the fade do the work.
- ✓Step back to judge. Look from a normal distance in daylight, not with your nose on the paint.
Sources and Related Reading
Previous and Next Lessons
About the Author
This lesson is written by the team at Ace Auto Body Inc. in Hackensack, New Jersey, an auto body repair and paint shop, with about 20 years of experience behind KJ Lee's work. We share real repairs from our shop, with our own diagrams, so car owners can understand what a proper repair involves. Read more on the About page.
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