The honest answer: “Leakproof” depends on 4 things
Silicone bags can be extremely leak-resistant, but “truly leakproof” depends on:
- Closure type (pinch-lock, slider, zipper track, clamp)
- How full the bag is
- What you packed (thin liquids vs thick foods)
- Pressure & movement (commutes, flights, a bag being squeezed)
If you want to carry soups or sauces confidently, use the checklist below.
What makes a silicone bag leak (most common causes)
1) Overfilling
If the bag is too full, sealing pressure becomes uneven and liquid can reach the closure line.
Rule of thumb: leave at least 20–25% headspace for liquids.
2) Tiny crumbs/oil in the seal
A single grain of rice in the seal track can break the seal.
Fix: wipe the seal area clean and dry before closing.
3) Uneven closure (not fully snapped)
Some pinch locks need a firm press along the entire length.
Fix: press from one end to the other slowly.
4) Thin liquids + squeezing pressure
Even a good seal can be challenged if the bag is stuffed in a backpack and compressed.
Fix: secondary containment + packing strategy (below).
Leakproof sealing routine (30 seconds that prevents 90% of spills)
- Fill the bag (don’t overfill).
- Wipe the seal area (inside edges) with a clean towel.
- Close slowly from end to end.
- Run your fingers across the seal twice to confirm full engagement.
- Do a quick “tilt test” over the sink.
How to pack soup or broth without spills
Best method: “Freeze-flat” soup packs
This is the easiest, safest way to transport soup.
- Let soup cool to room temp.
- Pour into the bag (leave headspace).
- Seal carefully.
- Lay flat on a tray and freeze.
- Once frozen, store upright like files in a freezer bin.
Why it works: A frozen sheet doesn’t press against the seal like sloshing liquid.
If you need to pack liquid soup fresh (not frozen)
Use a “double protection” method:
- Put the silicone bag inside a small hard container (or a second zip bag)
- Store the bag upright in your lunch bag
- Avoid placing heavy items on top
Pro tip: Pack thicker soups (lentil, pumpkin, chowder) for less slosh than thin broth.
Packing sauces, dressings, and marinades
- Choose thicker liquids when possible
- Leave headspace
- Wipe and seal carefully
- Use secondary containment if traveling
For marinades: squeeze out excess air so the food is surrounded, then seal. Always place the bag on a plate/bowl in the fridge (extra insurance).
Travel & commute: how to stop pressure leaks
Backpack commute
- Store upright
- Put in a corner of the bag so it’s not squeezed
- Use a hard lunch container as a “shield”
Flights
Cabin pressure changes + bag compression can cause leaks.
- Avoid carrying thin liquids in a silicone bag alone
- Freeze first if possible
- Always place in secondary containment
“Leakproof test” you can do at home
Before trusting a bag for soup:
- Fill with water to typical liquid level
- Seal carefully
- Turn upside down over the sink for 30 seconds
- Gently squeeze the body (simulate a backpack)
If it drips, it’s not ready for liquids—or your sealing method needs adjustment.
How to improve leak performance with smarter packing
- Use silicone bags for semi-liquids (stews, chili, thick soups)
- For thin broths: freeze-flat or use a rigid container
- Always keep the seal clean and dry
- Don’t overfill
Quick FAQ
Are all silicone bags leakproof?
No—closure design and quality vary. Look for strong closure feedback and consistent sealing.
Why does mine leak only sometimes?
Usually crumbs/oil in the seal, uneven closure, or the bag being squeezed.
Can I put hot soup directly in?
Let it cool first. Hot liquids produce steam pressure and can stress the seal.