Why is it printing like this?

Looks like it might be wedding stationery, you have to pay more for that.

Is it the In-laws' printer?

Looks like Gods’ knackered it

Disappearing ink?

What make and type of printer is it?

Try changing the text colour to a dark blue - that way Cyan, Magenta and Yellow will be used too.

Could just be the black print head that's buggered. The shape of those lines doesn't look consistent with head problems though. They are usually linear and uniform in pattern.

I've owned a lot of inkjets from all the big manufacturers and they have all ended up doing that especially if they are not used regularly (daily or weekly). They clean themselves each time you turn them on/off by wasting vast quantities of your very expensive ink, so if you don't cycle them they dry out and block the printheads which are built into the printer or print head (depending on manufacturer. Sometimes you can clear it with several cleaning cycles or flushing through the head (if it's built into the printer) with cleaner, other times the head is caput and you need a new head/printer/cartridge.

I eventually gave up and bought a home laserjet which is utterly reliable but only black and white. IF anyone wants colour they can look at it on the internet IMHO.

It's an HP officejet 6230

Have you used non-HP ink cartridges?

Let’s address the elephant in the room.

You know some of god’s relations?

So an HP will replace the print head when you get new ink, so should fix the problem, unless the interconnect between the head and rest of the printer is damaged, which I've never seen.

But given the cost of a new cartridge Vs a new printer it may be cheaper just to buy a new one, and sign up to the ink subscription plan.

The 6230 just takes ink, it has a built in print head by the looks of the cartridges. Try IPA or brake cleaner on the print head (remove cartridges first). That looks partially blocked.

As the others said, normally the print head is disposable i.e built into the cartridge, so a new cartridge will be a new print head.

You know some of god’s relations?<br /><br />

maybe it’s a hit list 

HP used to do print heads in the cartridge, but more recently they haven't. Our current 'HP Ink' subscription printer has cartridges with no head.

I'd use water on a cotton bud if you're going to try cleaning the heads. The ink is water based which is why it sticks to your hands.

We used to use paper to clean print heads as it's the material it's designed to touch. Newsprint is good as it has loads of detergent left in it (also great for glass as a result). Just wrap it around some folded up kitchen roll, make it damp with a spray of water then carefully rub the print head over it. Then we'd make up a test sheet like a de stijl artwork with heavily contrasting colours and get it to spew that out a few times along with a few pages of quick brown fox.

Which bit do I clean?

The printing is for signs for Christmas card stock. Mystery over.

The nozzles are made in a very thin sheet of kapton which will be a transparent brown colour. They are very delicate and there will also be (probably) a non wetting coating applied to the kapton, which can be rubbed off. I would use a cotton wool bud and very gently wipe the surface of the kapton.

You will need to take the cartridge out of the printer to clean it 

I never knew until now that there was such a thing as a godbrother or godsister.

You learn something new every day.

there is a way of getting the printer to perform some self cleaning and then some deep cleaning - it's happened to me twice when the printer has not been used in a while.

took longer to find the access into the process on the printer

Settings   Printer  Printer Properties  Maintenance Tab  Clean or Deep Clean - print test page - does it all itself and my printer is donkeys old

Urgh, looks like its not intended as a user serviceable part. That said printheads are only about £20. 

(881) How to change printhead on HP Officejet 6810 6820 6830 Printer CQ163-80060 - YouTube

I’ve owned a lot of inkjets from all the big manufacturers and they have all ended up doing that especially if they are not used regularly (daily or weekly).

My HP does not do this, although previous Epson ones did. We've had it years, used very irregularly, seems to be unstoppable.

I'm not sure that's blocked print head though as each line has at least some full print parts in it. Looks like it might be just buggered.

It aspires to be a graphic designer for early 2000s hipster magazines.

Never understood why cards need to be relation-specific.
🤔

Do you do a second-cousin-twice-removed, good luck in your new home one?

Kayak, Christmas is a nightmare.
Mum and partner.Dad and partner. Daughter and partner and every combination of people under the sun.
Mother's day is going ****ing stupid as well...you're like a mum to me ...blah blah blah.

Could be some dust in the print head that's moving around. Or an air bubble. Or damaged non wetting coating causing the face of the nozzle to flood. 

zippy - I have godless children and godless grandchildren - got any cards for me?

(I take on some of the godparent role but cannot be an official godparent as I am not baptised hence godless parent  Their mother was religious)

Long term solution; buy a cheap laser printer and never worry about this sort of crap every again.