User Guide
Frequently Asked Questions
From cleaning to cooking to storage — clear answers for every step of making fish scale collagen jelly at home.
1. Preparation
Do I need to wash the fish scales before cooking? How?+
Yes. Soak the fish scales in coarse salt and white vinegar for about 30 minutes, then rinse thoroughly with clean water.
The acidity of white vinegar helps remove impurities and residual protein from the scale surface, while coarse salt provides physical scrubbing and osmotic cleaning. Together they work best.
What is the water-to-scale ratio? When should I decide?+
The water amount must be decided before you start cooking. Do not add water during or after cooking.
| Cooking Method | Water per 500g Scales |
|---|---|
| Gas stove | 3 litres |
| Slow cooker | 3 litres |
| Pressure cooker — valve open | 3 litres |
| Pressure cooker — valve sealed | 2 litres (sealed = no evaporation) |
For 1kg of scales, double the water accordingly. Beginners should follow the standard ratio first, then fine-tune with experience.
Do I need to pre-soak the scales beforehand?+
No extra soaking is needed. The 30-minute soak in coarse salt and white vinegar is the cleaning step. After rinsing, cook directly.
2. Cooking Methods
How do I cook with a gas stove?+
Use 3 litres of water per 500g of scales. Bring to a boil on high heat, then reduce to low heat. Maintain at least 80°C throughout. Simmer for a minimum of 2 hours, up to 3.5 hours. During cooking, the scales will gradually curl and the broth will become thick and sticky.
Can I use a slow cooker? What should I watch out for?+
Yes, but you must pre-boil on a stove first to reach the required temperature before transferring. Slow cookers heat up slowly, and some models on low settings can't consistently reach 80°C — starting from cold water will prevent collagen from being extracted.
- 1Boil on high heat on the stove for at least 15 minutes
- 2Once temperature is confirmed, transfer to the slow cooker
- 3Continue slow cooking for 2–2.5 hours
How do I cook with a pressure cooker? Valve open or closed?+
A pressure cooker heats up fast enough on its own — no pre-boiling needed. You can start directly.
| Valve Position | Water Amount | Cooking Time |
|---|---|---|
| Valve closed (sealed) | 2L per 500g | 45–50 minutes |
| Valve open | 3L per 500g | About 2.5 hours |
Cooking time comparison across methods?+
| Method | Reference Time |
|---|---|
| Gas stove | Min. 2 hours, max. 3.5 hours |
| Slow cooker (from transfer) | 2–2.5 hours |
| Pressure cooker — valve closed | 45–50 minutes |
| Pressure cooker — valve open | About 2.5 hours |
3. How to Verify Success
How do I know if the collagen has been extracted?+
There are three phenomena you can verify with your own eyes — no lab report needed:
Scales curl up
During cooking, the fish scales will gradually curl.
Broth becomes thick and sticky
When scooped with a spoon, it's thicker than plain water. A dab on your finger feels noticeably sticky.
Gels after refrigeration
After bottling and refrigerating overnight, it turns into a jelly-like consistency the next day.
Will the broth turn white?+
No noticeable colour change. The correct indicators are the broth's thickness and stickiness, not colour. Don't judge success by colour — it's misleading.
The gel is soft — is that a failure?+
No. Gel firmness varies depending on water ratio, cooking time, and fridge temperature. Both soft and firm gels mean the collagen was successfully extracted. What matters is that it gelled, not how firm it is.
4. Troubleshooting
The broth is still watery after cooking — what went wrong?+
The three most common causes:
- 1Too much water — wrong ratio, collagen diluted.
- 2Temperature too low — didn't maintain 80°C throughout, especially if using a slow cooker without pre-boiling.
- 3Cooking time too short — collagen hasn't fully released yet.
The scales didn't curl — what should I do?+
Scales not curling usually means temperature was too low or cooking time was too short. Check that the temperature stayed above 80°C throughout and that cooking time met the minimum requirement.
If using a slow cooker, confirm you pre-boiled on the stove for at least 15 minutes first.
After stove cooking, the water barely reduced — is that normal?+
With a stove or slow cooker, water volume should reduce by about 30–40% through natural evaporation. If it barely reduced, the flame may have been too low or the lid was sealed too tightly, preventing steam from escaping.
With a sealed pressure cooker, water doesn't evaporate — volume stays the same, which is normal.
5. Bottling & Storage
How do I bottle and refrigerate after cooking?+
Follow these steps in order — each has a reason:
- 1Pour the cooked broth into glass bottles (sealed lid type recommended)
- 2Loosely place the lid on top — don't tighten — let steam escape while keeping dust out
- 3Let it cool at room temperature for about 30 minutes
- 4Once cooled, tighten the lid to seal
- 5Refrigerate on the main shelf (middle or upper), with space between bottles
- 6Check for gelling the next morning
Why not tighten the lid immediately while hot?+
Hot broth produces steam. Sealing immediately causes pressure changes inside the bottle, affects the seal, and may make the lid hard to open later. Loosely placing the lid lets steam escape naturally while keeping dust out. Tightening after cooling gives the best seal.
Can I put it straight into the fridge, or must I cool it first?+
You can, but it's recommended to cool at room temperature for about 30 minutes first. Putting a hot bottle directly in raises the fridge's internal temperature temporarily, may affect surrounding food, and can cause uneven gelling. The 30 minutes is a recommendation, not a strict rule.
Where in the fridge is best?+
Place on the main shelf (middle or upper level). Do not put in the crisper/fresh drawer — it's slightly warmer and may not be cold enough for proper gelling.
How long does it keep in the fridge?+
Consume within 2–4 weeks, depending on fridge conditions. The more stable the temperature and the tighter the seal, the longer it lasts.
6. Common Mistakes
| ✕ Wrong | ✓ Correct |
|---|---|
| Adding water during or after cooking | Decide water amount before starting — no additions |
| Starting slow cooker from cold water | Pre-boil on stove for 15 min, then transfer |
| Sealed pressure cooker with 3L water | Sealed: only 2L per 500g scales |
| Judging success by broth colour | Judge by stickiness, thickness, and gelling |
| Treating soft gel as a failure | Soft or firm — both are success |
| Tightening the lid immediately | Loosely cover, cool 30 min, then tighten |
| Placing bottles in the crisper drawer | Main shelf, with space between bottles |
Lots of foam when washing the pot — is it chemicals? Are the scales chemically processed?+
This foam has absolutely nothing to do with chemical processing. It's caused by collagen protein residue left in the pot. Protein molecules are partly hydrophilic and partly hydrophobic — when water hits the protein residue on the pot walls, it naturally traps air and forms foam.
The same thing happens when washing a pot used for bone broth, fish soup, or boiling eggs. It's a completely natural protein reaction — no chemicals involved.