If you landed here directly, this is the link to the first of this series of The complete industrial designer.
Once you have the brief after user research, you'll want to start by making one beautiful drawing. Don't.
Instead, give me forty, and give them by lunch because the first ten ideas will be ones everybody has. And they'll turn up fast because they're already in your head from every bottle you've ever seen, and getting them out is the job of the first thirty to sixty minutes. Somewhere around eleven to forty is where you start making things up instead of remembering what you'd seen on Pinterest.
Which means I don't want sketches from you, I want twenty plus pages of everything that's in your head and that's when things will start evolving. Doing it in thumbnail size helps a lot. We used to do it in our early days of software design. Designing things in thumbnail size. A thumbnail is only about 50mm across and you can't put any detail, so it'll force you to draw just the thing that actually separates one option from the next at this stage, which is proportion and stance and shape and basic construction. I mean nobody picks a direction based on a fillet radius, right?
Pre-requisites
The volume of water is important. It's what will be the core decider of the form. A litre of water volume will decide how fat you let the bottle get.
With about 74mm inside, the water column will come to around 232mm tall. If you make the wall wider to 80mm, the height drops to about 199mm. If you make it go till 88mm, the height drops further to 164mm. Why would this be important? Because you'd be making headspace above the fill line, and the neck, and the cap, and whatever the base needs.
An 80mm body with about 25mm of neck and headspace and a cap around 45mm lands somewhere near 270mm tall, and that's a decent bottle. Take it to 74mm to make it look slimmer and the same bottle goes past 300mm, and it stops fitting properly in most fridge doors, which are often only about 200mm of clear height.
So don't treat the section as a formality. Picking the diameter is key as it decides almost everything else on the project.
Print it at three sizes, tape tracing paper over it, and sketch through it. Every thumbnail you do after that is a bottle that could actually exist.
Draw forty ways of opening first
I'm repeating the forty but it's a random number only meant to represent quantity of explorations.
Okay. Start with the portion of the bottle which will have the maximum amount of user interaction - the cap. So that's what we should focus on first and get on the sketches. Where the button sits, whether it's on the front or the top or under an organic-shaped lip. Whether the cap hinges back or does it slide, or does it life? Whether the buckle is a hook or a latch under a rim? Whether the spout is round or oval, whether it stands extruded, and where the seal ends and when the cap opens, is it touching something else in the cap or not.
Draw the body too because the interaction with the cap is while holding the body. Change one thing in every sketch iteration, evaluate it, and change it again to improve.
Solve the grip
A hand wraps comfortably round something roughly 60 to 75mm across. Anything beyond that makes it a bit uncomfortable. I mean, people would still hold it with their fingers spread and palm flat against the side which is okay but not great. May
Which is why many bottles put a loop on the cap and Stanley put a handle on the side. So don't add the hook later. Draw it along with the main bottle body for grip as they're solving the same problem of grip. The trade-offs here to deal with would likely be height vs. diameter vs. a grab handle or loop or hook.
Do a ton of variations here as this is really what brings the bottle together and will give it the signature look.
Step back and start doing sharper sketches
What are the key questions we're trying to answer by now? They are sharper now.
Where the button sits? How do you intend the users to carry the bottle? What should be the diameter of the bottle? Where should the CMF band fall?
Does the button sit on front or top or under a lip or on the hinge itself? Do you carry the bottle with a cap loop or a side handle or a waist or a a carabiner hook? For a 1-litre bottle, Is the diameter most comfortable at 74mm, or 78mm, or something else? And then, with a clear body with coloured parts for personalisation and brand identity, should the placements be horizontal in divisions or proportionately somewhere else in the body?
Sketch one change at a time on a full size outline with a hand outline over the top of each outline. With different diameters next to each other at full size, we can make decisions in minutes.
With the above method, your sketches will also be organised now as they follow a natural grouping.
Write a part count on every sketch or thumbnail
Somewhere around the fortieth, start putting a number next to each one, which is how many separate parts the bottle needs.
For instance, a click-open cap is more parts than a screw cap and that's the price of the thing. Cap body, hinge pin, button, spring, latch, spout seal, and a thread seal underneath, so about seven. This will start becoming real now and you'll start sketching towards fewer parts. It reduces cost, yes, but fundamentally, one less joint is also one less joint where water could get trapped.
Once you put numbers, you'll start getting influenced as well. It'll start changing your preference towards which ones you like. Which is also the point. This activity will push you to sketch ideas that don't exist normally.
Very likely, you'll proceed with 3-quarter section views, to illustrate different details of each intersecting parts, ratios, thickness, texture, profiles, and so on. So I'm not getting into those how-tos. In sketching, obviously, illustrate how water is half-filled or full or partially filled and how the look changes.
What the sketching activity should deliver
The package section first, with the litre and the inner diameter and the water column and the headspace and the neck and the cap, taped under tracing paper at three sizes. They should also have part count for each iteration shown.
The four decision points from earlier drawn at full size, covering button position with a thumb on each, how you carry it, body diameter with a hand outline over the top, and where the bands or loop or hooks fall.
Keep every exploration and keep them categorised.