In short: Fit the tip before you fill the bag. Cut the end so about a third of the tip comes through and its wide base rests against the inside. Cut too much and the tip pops out; cut too little and frosting escapes around the edges.
Which piping bags to use
Reusable fabric bags. Not recommended: bacteria remain in the fibres even after careful washing.
Thin disposable bags. Fine for light creams and short jobs, but they tear under a stiff buttercream.
Thick disposable bags. The everyday working choice: they hold pressure, do not slip in the hand and take a coupler well.
Step by step
- Drop the tip into the bag, narrow end down, and push it as far as it will go.
- Mark where the tip reaches and cut the bag there — about a third of the tip should come through.
- Push the tip back into place so its wide base sits against the inside of the bag.
- Fold the top of the bag outwards and fill it no more than halfway.
Cut conservatively: you can always trim more, but a bag cut too wide is finished.
Why use a coupler
A coupler is a two-part ring: the wide half sits inside the bag, the narrow half screws on outside and holds the tip. It lets you change tips without emptying and refilling the bag — worth it as soon as one dessert needs two or three different patterns.
Frequently asked questions
Where do I cut the piping bag
At the point where about a third of the tip comes through. Insert the tip first and mark the line against it.
Why does frosting leak around the tip
The cut is too wide and the tip is not seated tightly. Take a fresh bag and cut less — you can always trim more.
How full should a piping bag be
No more than half. An overfilled bag pushes frosting out of the top and you lose control of the pressure.