Should I repeat character descriptions if a minor character reappears the second time too far into the story?
For example, I have a minor character who is introduced and has a bit of involvement at the start of the novel, but comes back in the third act and stays with us till the end. I've described him the first time he appeared, and my question is, do I need to do it again because my readers may have forgotten what he looked like by the second point we see him?
Elaborate or remind, but try not to repeat yourself.
Let's say you introduce a character early on in your story:
Protagonist opened for a handshake, but Character simply stared at their hand, as if it were too much effort. They looked miserable, with dark messy hair, washed out clothes and scuffed shoes.
Then, you meet the character again. It has been most of the book since you met them.
Character was just as anti-social as last time. Protagonist smiled as warmly as they could. Character's hair was the same dark coloured mess and though their suit was still absent of colour, their shoes were only more scuffed and marked, almost giving them more personality.
The idea is to remind the reader of what the protagonist already knows, not what the reader should remember, even though your goal is actually the latter. Most readers will remember when prompted, or will simply acknowledge that this has already been stated.
As a reader with a memory like a sieve, I really appreciate being reminded of character and location descriptions, especially when they tell me even more about someone. In my example, the elaboration of the second paragraph would not have the same effect without the first paragraph. Use that to your advantage.
Edit:
What I meant by "do not repeat yourself" is to avoid saying the exact same thing. If our second paragraph read as:
Protagonist smiled as warm as they could. Character was just as anti-social as last time. They looked miserable with dark messy hair, washed out clothes and scuffed shoes.
Then readers who do remember will gain very little from the description and even feel patronised - which I imagine is your concern - so make sure you vary the description, even if you are admitting that you've told the reader this before.
I wouldn't repeat them, but there's nothing wrong with referring to the description to remind the reader (though there's a good chance this is what you meant - apologies if so).
If your character has hair which is - in the earlier section - "so grey that it was almost white", when he reappears this can become "the shockingly silver hair that made him unforgettable".
You're right that some readers will have remembered and others won't, so referring to the earlier description without using the same words should let those who have remembered feel they are learning something new, and those who had forgotten will be reminded of details they might earlier have missed.
I would not repeat the description in any precise manner, but the same kind of quick thought summary a normal character might have, after whatever length of time has passed. Just enough thread to remind the reader, that probably feels the same way (but read your description a few day or a week ago).
He looked familiar, and Ann realized it was that tall shopkeep in Alfordshire they'd met months ago.
Brian? No, Byron. What's he doing here?
Your characters may very well have forgotten, or almost forgotten, about this character if enough happened in-between and his role was not too magnificent. This gives you as the author the chance to repeat the most important things. If one of your characters is one who lives in the present and easily forgets stuff that he deems unimportant he might have forgotten about this person and therefore asks another character "Who is this guy?", which allows you to summarize the most important points from the perspective of one of the other characters for example like "You mean John? John, who helped us that one time we being followed by enemy spies? You really want to tell me you forgot about the chase?" to which character number 1 could answer "Ah, the chase! I remember now. Fun times."
Or maybe one of your characters doesn't know who the guy is that always wears a shirt with a pop-culture reference and talks like he is from the last century - simply because he never met him and nobody ever mentioned him. This gives you the chance to use the characters that have already interacted with the character to summarize the most important points about Mister Timetraveller to your newer characters.
Another option would be to remind the reader some time in-between. When your heroes are sitting around the camp fire and reminisce about that one time they met this guy with the mustache that seemed to have a life of its own, wondering what happened to him after they left him at the ruins.
By making it a summary those readers that already remember the guy won't feel like they being told the exact same thing again and those readers that have forgotten will be reminded of him. If they have completely forgotten about the character they will at least know the important things about this character again and therefore not feel like they are missing something from the story.
You should try to give him a few key features that are easily remembered. A certain way to speak, certain clothes, remarkable physical aspects... maybe just a remarkable thing this character did that your characters will forever be grateful about. Depending on your story you could make your characters think he was dead and thereby remember his great heroic deeds that saved them - just to see him a few days later at the market.
Maybe the character has a new scar that allows him to remind the group of the story. "Hello, Mister Goaty! I thought you were dead. How did you make it out alive?" to which he remarks "Ah, my little sheep! It's good to see you again. Those pesky undead don't stand a chance against someone as mighty as me! ... ", pointing at a big jagged scar on his shoulder "Though their leader did land a pretty good blow. Nothing to worry about though. What happened to you my friends while I was gone?"
Just make sure you don't let the repeated description take the place of saying who the character is. In Wheel of Time Jordan lavishes page after page on mustaches that curl or how many petticoats are worn under skirts or who wears a leather bracelet or whatnot and then 4 and a half books after we last saw a character it's "nobody noticed the man at the back with the curly mustache who slipped away before the dancing was done" or "in the background a man in a blue coat limped away" and we're supposed to know who it is.
Generally I prefer description if it serves a purpose, like letting us know this character's background, or what's important to them. Eye colour and such are only important if they are really important in the world you're building. So if you are going to repeat anything from the first time around, make sure it's something that's relevant -- like being impeccably groomed, or having very expensive shoes, or being so much taller than everyone else. Or find a way to make it important: "his bright blue eyes were as improbable as she remembered, and she fought the urge to just stare into them to experience that colour completely."
If the readers have seen the character before, but the characters in this scene haven't, then your choice is either to describe the character long enough that readers finally remember who we're talking about, then introduce them, or to introduce them right away and have the other characters react to the appearance (assuming them to be poor, well educated, foreign, or whatever) with a tone that implies the readers already know about the shoes or the eyes or the height or whatnot.
Let another character describe him. This way you do not repeat yourself, because it's thoughts of someone in the novel.
This was the first time the two met. Bob has been told that Character was a skinny, tall, guy, but face to face, he looks like a tower compared to all the other people in the room, all this pronounced by his dark hair and contrasting green eyes.
