# How do I fix blobs and zits?

Blobs and zits come from seam pressure. Tune pressure advance, retraction, and where the seam sits, and dry the filament before you blame the spool.

A zit at the start or end of a loop is unused pressure at the seam. Sanding it off works once. The consensus tunes the pressure instead.

## Order of work

Dry the spool. [PolyLite PLA](/brand/polymaker/polylite-pla) lists 55 °C (131 °F) for 6 h. Other rows may not list hours. The bands by material are on [drying](/answers/drying).

Then retraction, inside the extruder’s band. Direct drive is about 0.5–1 mm on the [ooze page](/answers/ooze). PLA Basic’s sheet lists 0.6–1.0 mm. A longer retraction can trade a zit for a clog.

Then pressure advance, also called linear advance. [How to calibrate flow and pressure advance](/answers/flow) is the sequence, including the temperature tower. This page does not have a K value to type in.

Then seam placement. Park an aligned seam on a rear corner you can sand. Random seam is a scatter, not a cure.

## What the ranked rows are for

[Prusament PLA](/brand/prusament/pla), [PLA Basic](/brand/bambu-lab/pla-basic), and [PolyLite PETG](/brand/polymaker/polylite-petg) are examples of spools you calibrate one at a time. None of them store pressure advance. A profile that looked clean on one of them can zit on the next because the advance value moved with the spool.

Updated 2026-10-15. Sources accessed 2026-10-15. Use case: Troubleshooting.

## Ranked filaments

| Rank | Filament | Nozzle | Bed | Price per kg |
| --- | --- | --- | --- | --- |
| 1 | Polymaker Polylite PLA | 190–230 °C (374–446 °F) | 25–60 °C (77–140 °F) | — |
| 2 | Prusament PLA | 205–225 °C (401–437 °F) | 40–60 °C (104–140 °F) | — |
| 3 | Bambu Lab PLA Basic | 190–230 °C (374–446 °F) | 35–45 °C (95–113 °F) | — |
| 4 | Polymaker Polylite PETG | 220–250 °C (428–482 °F) | 70–90 °C (158–194 °F) | — |

## What the community says

The consensus is that zits and blobs come from seams and pressure. Tune pressure advance, retraction, and seam placement, and dry the filament.

## Sources

- [Bambu PLA Basic technical data sheet V3.0](https://cdn.shopify.com/s/files/1/0584/7236/6216/files/Bambu_PLA_Basic_Technical_Data_Sheet_bf3411ce-be39-4db7-9669-1b4671d2196b.pdf?v=1734060943) (datasheet)
- [PolyLite PLA technical data sheet](https://cdn.shopify.com/s/files/1/0548/7299/7945/files/PolyLite_PLA_TDS_EN_V5.4.pdf) (datasheet)
- [PolyLite PETG technical data sheet](https://cdn.shopify.com/s/files/1/0548/7299/7945/files/PolyLite_PETG_TDS_EN_V5.4.pdf) (datasheet)
- [Community source, r/BambuLab 1kpfdwo](https://www.reddit.com/r/BambuLab/comments/1kpfdwo/) (reddit)
- [Community source, r/FixMyPrint 1mbigcb](https://www.reddit.com/r/FixMyPrint/comments/1mbigcb/) (reddit)
- [Community source, r/3Dprinting va8t4p](https://www.reddit.com/r/3Dprinting/comments/va8t4p/) (reddit)
- [Community source, r/3Dprinting 10lyhx4](https://www.reddit.com/r/3Dprinting/comments/10lyhx4/) (reddit)
- [Community source, r/FixMyPrint zz67i6](https://www.reddit.com/r/FixMyPrint/comments/zz67i6/) (reddit)

HTML: https://filamentfacts.com/answers/blobs