Liquid Culture & Agar Recipe Calculator
Calculate precise ingredient amounts for liquid culture broth and agar recipes — scaled to your exact batch size. Choose LC or agar mode, select your recipe, enter the volume you need, and get gram-accurate measurements for every ingredient. Covers honey LC, karo LC, malt extract LC, MEA agar, PDA agar, and nutrient agar with sterilization parameters for each.
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Recipe notes
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Select a recipe to see notes.
Common LC and agar mistakes
- Over 4% sugar in LC. Higher sugar concentration creates an environment where contaminating bacteria outcompete mycelium. Keep honey, karo, and malt extract LC at or below 4% (4g per 100ml). The calculator enforces this — recipes above 4% are not included.
- Adding agar powder to boiling water. Add agar to cold or warm water and bring to a boil while stirring. Adding agar powder to boiling water creates clumps that don't dissolve properly. The result is uneven agar with soft spots that support bacterial growth.
- Pouring plates while too hot. Agar poured above 130°F (55°C) causes condensation on the plate lid as it cools, creating water droplets that pool on the agar surface. Wait until the flask is just barely comfortable to hold (around 105–115°F / 40–46°C) before pouring plates.
- Not checking LC for contamination before use. Contaminated LC spreads contamination to every jar it touches. Hold the jar against a light source and look for cloudiness, strands, or color changes. Healthy mycelium LC should be clear or very slightly cloudy white. Any yellowing, green, pink, or foul smell = discard the entire jar.
Recipe
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Ingredients
Sterilization
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Inoculation
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Make your first LC or agar batch in four steps
Choose LC or agar and select your recipe
Liquid culture is for inoculating grain jars — it delivers mycelium directly suspended in liquid, colonizes grain faster than spore syringes, and can be expanded indefinitely from a single clean source. Agar is for cloning fruiting bodies, isolating clean genetics from spores, long-term culture storage, and making agar-to-agar transfers. If you're just starting out: make a honey LC first, verify it colonizes cleanly, then move to agar work once you have a clean genetic source to clone from.
Weigh ingredients to the gram and prepare your jar
Use a kitchen scale accurate to ±0.1g — LC and agar concentrations matter. Dissolve sugar or malt in distilled water (not tap — minerals affect growth and sterilization). For agar, add the powder to cold water and stir while heating to avoid clumps. Use a wide-mouth jar with a filter patch lid (polyfill or tyvek) that allows gas exchange. Magnetic stir bars are useful for LC jars — they allow post-sterilization mixing without opening the jar.
Sterilize at 15 PSI for the time shown
LC and agar sterilize faster than grain because they're liquid-phase — heat penetrates in minutes rather than the 30+ minutes required for dense grain. The time shown is from when pressure reaches 15 PSI, not from when you light the burner. For agar, set up a sterile poured-plate station before sterilizing so you're ready to pour as soon as the flask cools to 105–115°F. Use the Sterilization Time & Pressure Calculator for full step-by-step guidance if this is your first run.
Inoculate in still air — check LC for contamination before using
LC: inoculate with spore syringe or agar wedge in a still air box. Shake or stir daily. Before using LC to inoculate grain, hold the jar against a bright light — healthy mycelium LC is clear or slightly cloudy white with visible white stringy growth. Any cloudiness, color, or foul smell means contamination — discard. Agar: pour plates in still air, let set fully before inverting, store in sealed bag in the fridge. Use within 6–8 weeks for best results.
Why LC is better than spore syringes for grain inoculation
Spore syringes start the colonization process from individual spores, which must germinate, find a compatible mating partner (for heterothallic species), and then begin growing. This takes 5–14 days before visible mycelium appears and carries genetic variability from spore-to-spore. Liquid culture contains already-germinated mycelium at a known density — it begins colonizing grain immediately upon introduction and consistently produces the same genetics as the source clone. LC-inoculated grain typically shows visible colonization in 3–7 days vs 7–14 days for spore syringes. For any serious grain spawn operation, making LC from a confirmed clean culture is worth the extra preparation step.
Why concentration matters, agar gelation, and how to read LC health
Liquid culture and agar are precision preparations — small variations in concentration significantly affect contamination resistance and mycelium performance. The recipes in this calculator are established community standards, not arbitrary. Understanding why each concentration is chosen makes it easier to troubleshoot and adapt. See the Spores & Cultures Guide for the full culture work reference.
4%
Maximum safe LC sugar concentration
Above 4% w/v sugar concentration, the osmotic potential of the broth begins to favor bacterial growth over fungal mycelium. Most contaminating bacteria thrive in high-sugar environments. Keeping LC at or below 4% balances nutrition for mycelium with contamination resistance.
2%
Agar gelation minimum
Agar powder gels reliably at 1.5–2% concentration. Below 1.5%, agar may not set firmly enough to support surface growth. 2% is the standard that produces a firm but not brittle surface — the right consistency for making transfers without tearing the gel.
105–115°F
Ideal pour temperature
Agar remains liquid until it cools to around 95–100°F (35–38°C). Pouring at 105–115°F gives a small window before setting while being cool enough not to cause condensation on the plate lid. Condensation on the lid creates water droplets that pool on the agar surface.
Reading LC health visually
Healthy LC contains white, stringy, or cottony mycelium suspended in clear or very slightly cloudy broth. The mycelium forms visible "strings" or "webs" that move when the jar is swirled. Signs of contamination: uniform cloudiness throughout the broth (bacterial contamination — bacteria are too small to see individually but cloud the liquid collectively); green, black, pink, or yellow coloration; foul or sour smell; slick or slimy growth rather than stringy mycelium; or lack of any visible growth after 2+ weeks at appropriate temperature. Any single one of these signs means discard — contaminated LC is not recoverable and will spread contamination to every jar it touches.
| Recipe | Best for | Contamination risk | Notes |
|---|---|---|---|
| Honey LC 4% | General purpose, cubensis, oyster | Low-moderate | Most forgiving recipe, widely available ingredient |
| DME LC 1% | Long-term storage, sensitive species | Lowest | Slowest growth, most contamination-resistant |
| DME LC 2% | All species, standard production | Low | Best balance of speed and reliability |
| MEA agar | Cloning, isolation, most species | Moderate | Go-to agar recipe for 90% of culture work |
| PDA agar | Slow-growing gourmet species | Moderate-high | High nutrient = vigorous growth but more contamination risk |
| Water agar | Genetic isolation, sector selection | Low | Stresses mycelium to reveal genetic differences |
Common LC and agar questions
How long does LC stay viable?
A clean, sealed LC jar stored at room temperature in low light stays viable for 3–6 months. In the fridge (35–40°F), viable for 6–12 months. Freezing LC is possible but requires cryoprotectant (10–15% glycerol added before freezing) — frozen without cryoprotectant, ice crystals destroy the mycelium. The practical approach: keep 1–2 jars at room temp for active use and refrigerate a "backup" jar per strain. When the active jar gets old or shows signs of degradation, expand from the backup before inoculating new grain.
Can I make LC from fruiting body tissue instead of spores?
Yes — this is tissue cloning, and it produces LC with identical genetics to the parent fruiting body. Take a small piece of inner tissue (not the outer surface — the inside is sterile) from a healthy mushroom using a sterilized scalpel in a still air box, drop it directly into LC broth, and incubate. The mycelium begins growing from the tissue within days. This is the standard method for preserving genetics from a particularly productive fruiting body. The LC made from a tissue clone can then be used to inoculate grain indefinitely.
My agar plates keep getting contamination — what's wrong?
Agar plates are the most contamination-sensitive work in mycology. In order of likelihood: (1) Not working in a still air box or flow hood — ambient air contains mold spores that settle on open plates in seconds. (2) Pouring plates while agar is too hot — warm air from the flask creates convection that pulls in ambient spores. (3) Plates not stored sealed in bags — agar surfaces contaminate through lids if exposed. (4) Agar under-sterilized. (5) Contaminated source culture transferred to plates. Solve problems 1 and 2 first — they account for 80% of plate contamination issues.
What's the difference between agar plates and agar slants?
Both are the same agar recipe poured into different containers. Plates (petri dishes) are used for cloning, isolation, and sector selection — the flat surface allows you to see and select specific mycelium zones. Slants are jars or tubes tilted at an angle while the agar sets, creating a slanted solid surface. Slants are used for long-term culture storage — the jar seal protects from contamination far longer than a petri dish. Most cultivators use plates for active work and slants for archiving important genetics. This calculator's volumes work for both — pour into your container of choice.
Culture work essentials
Successful LC and agar work requires clean ingredients, proper containers, and a sterile work environment. These are the items that matter most.
Agar powder & malt extract
Agar-agar powder ($8–15 per 100g), light dry malt extract / DME ($6–12 per lb). Buy food-grade agar powder — not agar flakes, which don't dissolve as cleanly. Light DME (not dark or specialty malt) is the standard for LC and agar. Store dry ingredients sealed in airtight containers — moisture contamination degrades both. A 100g bag of agar powder makes roughly 50 batches of MEA at 2% concentration.
Still air box & supplies
Still air boxes ($0 DIY from clear storage tote with arm holes, or $25–50 pre-built), 70% isopropyl alcohol ($4–8), alcohol lamp or butane torch ($8–25), scalpels and blades ($10–20). The still air box is the minimum clean work environment — it reduces ambient air movement to near zero during the critical period when containers are open. More important than any other single piece of equipment for LC and agar success.
Petri dishes
90mm plastic petri dishes ($15–25 per 20-pack), glass petri dishes ($20–40 per 10). Plastic disposables are the standard for home cultivators — cheap enough to use once and discard when contaminated. Use 90mm diameter for standard pours (15–20 ml each). Pour plates on a level surface and let set undisturbed for 15–20 minutes before moving.
LC jars & lids
Wide-mouth pint mason jars ($1–2), filter patch lids ($8–15 per 10), magnetic stir bars ($8–15 per 5). Filter patch lids allow gas exchange without contamination. Magnetic stir bars allow post-sterilization mixing without opening the jar — useful for dispersing mycelium growth evenly through the LC. Place jar on a magnetic stir plate for 30 seconds before drawing into syringes.
Precision scale
Digital scale, 0.01g resolution ($15–30). LC and agar preparation requires weighing to the tenth of a gram — a standard kitchen scale that reads to 1g produces meaningful error at small batch sizes. A 500ml honey LC at 4% needs exactly 20g honey — a scale accurate to ±1g could be off by 5%. For a 100ml test batch needing 2g DME, a 0.1g-resolution scale is essential.
Syringes & needles
10ml and 20ml luer-lock syringes ($0.50–1.50 each), 18-gauge needles ($0.30–0.80 each), needle caps. Syringes are used to draw LC from the jar and inject into grain jars. Use a fresh needle for each grain jar — needles dull quickly against polyfill filter patches and a dull needle contaminates more than a sharp one. Draw into the syringe inside the still air box, cap immediately.