A DIY food funnel made from 2-liter milk bottles. Two lids have been welded together using a hot knife and a hole has been cut through the top of both lids to make a screw connector between the funnel and the bottle.

DIY food funnel using hot knife welding

A DIY food funnel for filling milk bottles using welding with a hot knife cutter. drill.

Introduction

I use abundant 2-liter milk bottles, and vinegar bottles as food storage containers for both dry and liquid foods. They cost nothing, can be stored efficiently and can keep the food away from harm. To keep stored liquids sterile, I usually like to transfer the liquid into the storage bottle at a high temperature so that the content and the bottle are sterile. These opaque plastic bottles are made of HDPE and are quite stable even when filled with boiling liquids. “Yes, they go a little soft and wobbly, but they don’t shrink or collapse like many other plastics may do under a similar challenge.”

Most funnels, that can be used to fill such bottles, must fit inside the neck of the bottle. This greatly restricts the delivery diameter to about 20mm. This does not allow the free flow of coarse solids (eg rolled oats) or lumpy liquids (eg chunky pickles). An externally fitted DIY funnel as described in this post can have a much bigger delivery hole (~30mm) that will allow much easier filling.

Commercial funnels that can be used to fill 2 liter milk bottles for food storage.
Commercial funnels that can be used to fill 2 liter milk bottles for food storage.

This post describes how a hot knife cutter can be used to weld together two plastic milk bottle lids to make a free-flowing funnel connector. The DIY screw connector can be screwed onto the intact bottle and also onto a funnel made from another milk bottle.

Commercial funnels that can be used to fill 2 liter milk bottles for food storage. Alternative DIY funnels with wider exit apertures are shown on the right.
Commercial funnels that can be used to fill 2 liter milk bottles for food storage (~20mm exit aperture). Alternative DIY funnels with wider exit are shown on the right (~30mm exit aperture). The funnel on the far right has had the handle cut off to remove it as a trapping path for food. Some of the handle has been used to weld a patch over the hole left by the removal of the handle.

Making the DIY welded food funnel

The two lids can be held concentric with one another with an awl or a sought sewing needle. Then three tack weld can be made around the circumference to lock the lids together using the tip of a hot knife. This can be followed up with a continuous hot weld around the perimeter.

Initially, I used filler material that was cut from a sacrificial lid. However, as my skill developed, I could do both the tacking and the final welding without the use of filler and the result was much more elegant (shown in a photo near the end of the post).

The lids from two 2-liter milk bottles have been spiked together on a sharp awl in preparation for tack welding in three places around the welding zone.
The lids from two 2-liter milk bottles have been spiked together on a sharp awl to tack weld around the welding zone in three places. The strip of plastic shown is the rim of another lid that will be used as filler material for the welding.
The lids from 2-liter milk bottles after they have been welded together.
The lids from 2-liter milk bottles after they have been welded together.
After the lids from 2-liter milk bottles have been welded together a step drill has been used to cut away most of the lid tops so that a large opening is available for the passage of food through the funnel.
After the lids from 2-liter milk bottles have been welded together a step drill has been used to cut away most of the lid tops so that a large opening is available for the passage of food through the funnel.

Many similar bottles with slightly different threads

I don’t know why very similar milk bottles have slightly different threads. Anyway, screw connectors can be made to suit each different thread type. If the lids are all made of LDPE then lids with two different threads can be welded together to make suitable adaptors for the available bottles.

A DIY food funnel connector made from 2 liter milk bottles. Two lids have been welded together using a hot knife and welding filler melted from a scrap of plastic from another lid.
A DIY food funnel connector made from the lids off 2-liter milk bottles. Two lids have been welded together using a hot knife. In this case, welding filler melted from a scrap of plastic from another lid has been used to make the weld.
DIY screw connectors for connecting a DIY funnel to a 2 liter milk bottles for food storage. In these cases, the weld has been made without the use of filler material. The connector on the right is made with lids with two different threads so that it can be used as an adapter between a bottle and a funnel with slightly different threads.
DIY screw connectors for connecting a DIY funnel to a 2 liter milk bottles for food storage. The welds on these were made without the use of filler material and they are a lot neater. The connector on the right was made with lids with two different threads to be used as an adapter between a bottle and a funnel with slightly different threads.
A DIY food funnel made from 2-liter milk bottles. Two lids have been welded together using a hot knife and a hole has been cut through the top of both lids to make a screw connector between the funnel and the bottle.
A DIY food funnel made from 2-liter milk bottles. One bottle was cut off to form a funnel. Two lids have been welded together using a hot knife and a hole has been cut through the top of both lids to make a screw connector between the funnel and the bottle.

Vinegar bottles as an alternative storage bottle

So far, this post has focussed on 2-litre milk bottles because of their abundance. However, I have found that slightly more rounded and thicker vinegar bottles make an excellent alternative. They don’t pack quite as efficiently as square bottles, but their shape and thickness make them more resistant to rodent attack. “I think the little buggers can’t quite find any sharp corners to get started with their gnawing.”

The vinegar bottle and lid are also made of HDPE, but the thread is incompatible with most milk bottles. Consequently, two vinegar bottle lids can be welded together to make an alternative adaptor for a funnel made from a vinegar bottle. Luckily, I have plenty of vinegar bottles as I like to make pickled foods such as my pickled figs and fennel recipe.

Conclusion

These DIY milk bottle to DIY funnel connectors work much better than the commercial funnels. The use of this hot-cutting fabric knife is yet another welding application for this versatile and inexpensive tool.

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