Guitar Pick Materials and Equivalent Thickness

I was curious at equivalent pick thicknesses, and so I took a shot at calculating them, and it seems like most plastics are surprisingly close together. Did I make a mistake? If so, check out the program, and I’ll update it and fix any mistakes in the table. We basically are just doing the first formula on this page.

0.4mm Nylon 6/6 is roughly equivalent to:

  • 0.37mm Ultem
  • 0.38mm Acrylic
  • 0.39mm Delrin (Acetal)
  • 0.42mm Polycarbonate
  • 0.42mm Celluloid

0.5mm Nylon 6/6 is roughly equivalent to:

  • 0.46mm Ultem
  • 0.48mm Acrylic
  • 0.48mm Delrin (Acetal)
  • 0.52mm Polycarbonate
  • 0.53mm Celluloid

0.6mm Nylon 6/6 is roughly equivalent to:

  • 0.56mm Ultem
  • 0.57mm Acrylic
  • 0.58mm Delrin (Acetal)
  • 0.63mm Polycarbonate
  • 0.63mm Celluloid

0.7mm Nylon 6/6 is roughly equivalent to:

  • 0.65mm Ultem
  • 0.67mm Acrylic
  • 0.68mm Delrin (Acetal)
  • 0.73mm Polycarbonate
  • 0.74mm Celluloid

0.8mm Nylon 6/6 is roughly equivalent to:

  • 0.74mm Ultem
  • 0.76mm Acrylic
  • 0.77mm Delrin (Acetal)
  • 0.84mm Polycarbonate
  • 0.84mm Celluloid

0.9mm Nylon 6/6 is roughly equivalent to:

  • 0.84mm Ultem
  • 0.86mm Acrylic
  • 0.87mm Delrin (Acetal)
  • 0.94mm Polycarbonate
  • 0.95mm Celluloid

1.0mm Nylon 6/6 is roughly equivalent to:

  • 0.93mm Ultem
  • 0.96mm Acrylic
  • 0.97mm Delrin (Acetal)
  • 1.05mm Polycarbonate
  • 1.05mm Celluloid

1.1mm Nylon 6/6 is roughly equivalent to:

  • 1.02mm Ultem
  • 1.05mm Acrylic
  • 1.06mm Delrin (Acetal)
  • 1.15mm Polycarbonate
  • 1.16mm Celluloid

1.2mm Nylon 6/6 is roughly equivalent to:

  • 1.12mm Ultem
  • 1.15mm Acrylic
  • 1.16mm Delrin (Acetal)
  • 1.26mm Polycarbonate
  • 1.26mm Celluloid

1.3mm Nylon 6/6 is roughly equivalent to:

  • 1.21mm Ultem
  • 1.24mm Acrylic
  • 1.26mm Delrin (Acetal)
  • 1.36mm Polycarbonate
  • 1.37mm Celluloid

1.4mm Nylon 6/6 is roughly equivalent to:

  • 1.30mm Ultem
  • 1.34mm Acrylic
  • 1.35mm Delrin (Acetal)
  • 1.46mm Polycarbonate
  • 1.47mm Celluloid

1.5mm Nylon 6/6 is roughly equivalent to:

  • 1.39mm Ultem
  • 1.43mm Acrylic
  • 1.45mm Delrin (Acetal)
  • 1.57mm Polycarbonate
  • 1.58mm Celluloid

1.6mm Nylon 6/6 is roughly equivalent to:

  • 1.49mm Ultem
  • 1.53mm Acrylic
  • 1.55mm Delrin (Acetal)
  • 1.67mm Polycarbonate
  • 1.68mm Celluloid

1.7mm Nylon 6/6 is roughly equivalent to:

  • 1.58mm Ultem
  • 1.62mm Acrylic
  • 1.64mm Delrin (Acetal)
  • 1.78mm Polycarbonate
  • 1.79mm Celluloid

1.8mm Nylon 6/6 is roughly equivalent to:

  • 1.67mm Ultem
  • 1.72mm Acrylic
  • 1.74mm Delrin (Acetal)
  • 1.88mm Polycarbonate
  • 1.89mm Celluloid

1.9mm Nylon 6/6 is roughly equivalent to:

  • 1.77mm Ultem
  • 1.82mm Acrylic
  • 1.84mm Delrin (Acetal)
  • 1.99mm Polycarbonate
  • 2.00mm Celluloid

2.0mm Nylon 6/6 is roughly equivalent to:

  • 1.86mm Ultem
  • 1.91mm Acrylic
  • 1.93mm Delrin (Acetal)
  • 2.09mm Polycarbonate
  • 2.10mm Celluloid

I don’t know how to attach a file, so here you go

#!/usr/bin/env python3

from enum import Enum
from dataclasses import dataclass, field
from functools import total_ordering


class P(str, Enum):
    ACRYLIC = "Acrylic"
    CELLULOID = "Celluloid"
    DELRIN = "Delrin (Acetal)"
    NYLON = "Nylon 6/6"
    POLYCARBONATE = "Polycarbonate"
    ULTEM = "Ultem"


E = {
    P.ACRYLIC: 3.2e9,
    P.CELLULOID: 2.4e9,
    P.DELRIN: 3.1e9,
    P.NYLON: 2.7e9,
    P.POLYCARBONATE: 2.4e9,
    P.ULTEM: 3.3e9,
}

nu = {
    P.ACRYLIC: 0.35,
    P.CELLULOID: 0.35,
    P.DELRIN: 0.35,
    P.NYLON: 0.39,
    P.POLYCARBONATE: 0.37,
    P.ULTEM: 0.41,
}


def get_D(*, E: float, h: float, nu: float) -> float:
    return (E * h**3) / (12 * (1 - nu**2))


def get_h(*, D: float, E: float, nu: float) -> float:
    return ((D * 12 * (1 - nu**2)) / E) ** (1 / 3)


@total_ordering
@dataclass
class Pick:
    plastic: P
    h: float  # in meters

    E: float = field(init=False)
    nu: float = field(init=False)
    D: float = field(init=False)

    def __post_init__(self):
        self.E = E[self.plastic]
        self.nu = nu[self.plastic]
        self.D = get_D(E=self.E, h=self.h, nu=self.nu)

    @classmethod
    def from_D(cls, *, plastic: P, D: float):
        h = get_h(D=D, E=E[plastic], nu=nu[plastic])
        return cls(plastic=plastic, h=h)

    def __lt__(self, other: "Pick"):
        return self.h < other.h

    def __eq__(self, other: "Pick"):
        return self.h == other.h

    def __str__(self):
        return f"{self.h * 1000:5.2f}mm {self.plastic.value}"


def main():
    for hh in (0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,):
        h = hh / 1000  # now in meters
        nylon_pick = Pick(plastic=P.NYLON, h=h)
        matches = [Pick.from_D(plastic=p, D=nylon_pick.D) for p in P if p != P.NYLON]
        matches.sort()

        print(f"\n{hh:.1f}mm {P.NYLON.value} is roughly equivalent to:")
        for pick in matches:
            print(f"* {pick}")


if __name__ == "__main__":
    main()
2 Likes

As a physicist I can’t not like this.

And as a lazy person, I am extremely pleased by this:

PS: which one of the listed materials is closest to the material in Dunlop Tortex?

1 Like

I don’t see the material-depenfent coefficients you’re using on the Wikipedia page. Am I missing something? If not, where are they from?

I am a non-expert but think it is Delrin.

I dug up the material properties somewhat randomly but was surprised at how close they seem to be to each other.

The data analyst in me loves this, too.

Anecdotally, I do wonder if some of the coefficients are wrong, though - a 1.0mm Nylon Flow, to me, feels like the flex falls somewhere between an 0.88 Ultex and an 0.73 Ultex. I’d have figured somewhere around 0.8 would be the equivalent for a 1.0, though that’s subjective impression and not rigorous A/B, so grains of salt abound…

1 Like

I think the bendy-ness of the material only accounts for part of the pick attack Physics. Properties of the surface like texture friction etc can have a big impact too, both on the feel and sound… maybe that’s what accounts for the difference?

If me, specifically, then I don’t think so - I’m taking otherwise identical picks and simply bending them between my fingers, and I actually did go down to my studio room, grab a bunch, and really A/B/C/Y them last night to confirm - sujectively I was probably a little shy with that .8 guess, but a 1.0 Nylon is definitely between an 0.73 and 0.88 but closer to the 0.88. so, like 0.82? Vs a modeled 0.93.

This is awesome stuff nonetheless though, @kgk - thanks!

It is critical to compare experiments (actual bending) to predictions, please do that! But the recipe might be:

  • Decide how flexible you want your pick to be
  • Try various plastics right around that thickness for touch and tone.

I had expected a huge difference between materials, so I was really surprised that there is so little.

1 Like

hey, at a minimum, it’s a great jumping off point!

I’ll have some 1.14s in nylon in the next day or two, which in theory should be just as stiff as a 1.0 Ultex, though I don’t expect them to be. I’ll report back though once I do.

By the way, which of these materials is Tortex closest to? I have a bunch of those, too.

EDIT - just to clarify, I suspect your math is accurate, I just suspect the deflection coefficients you found aren’t. That’s not on you though and this is still very cool info!

1 Like

If the formula applies, it uses two very common material properties, so everything is easy to find… and the plastics seem pretty close to each other, so it could be that they’re still close despite proprietary additives.

I’m not a materials scientist but I don’t see an obvious mistake…

Tortex is delrin. The difference in texture is a finishing process.

2 Likes

Thanks Tom!

kgk - more to come once I have a bigger sample size, and compare some Tortex picks as well. I don’t know if I have a good way to scientifically measure deflection at a given weight I’m afraid, so it’ll have to be subjective, but… hopefully that still helps?

1 Like

Absolutely! The first question: do we have the correct order of plastics? Is nylon roughly in the middle? Are Ultem and celluloid the extremes? Is Delrin really close to nylon?

I bet we could come up with something that’s at least precise enough for our purposes. Would be better with larger pieces of the material in question, though, and frankly I’m not sure how much it matters for guitar playing because of all the extra variables mentioned above.

More testing than I did last night, lol. but for now, I did get the 1.14s in the mail, for me they feel perfect, and subjectively they’re between the 0.88s and the 1.0s, a little closer to the 1.0s, so maybe feels like a 0.95 Ultex…

…which checking my prior hunch that a 1.0 Nylon feels around 0.82, that would imply a 1.14 should feel like a 0.93, which as I’m just doing that math now that checks out pretty well with my subjective sense.

I’ll try to compare to some tortex picks tonight or over the weekend, but for now I have a bag of 72 of the 1.14s on the way - I even like the deep navy color more than the more primary blue of the 1.0s.