Learn Polish: Wprawdzie ten koc jest stary, ale jest cieplutki. - Admittedly this blanket is old, but it is nice and warm.

The suffix -utki turns the neutral adjective ciepły (warm) into cieplutki (nice and warm, or cozy). It adds a subjective feeling of pleasantness, comfort, or affection to the description. You will often see this suffix used to make adjectives feel more inviting.

Why does the ł in ciepły change to an l in cieplutki?

When adding the diminutive suffix -utki, the hard consonant ł softens to l. This consonant mutation is very common in Polish diminutives because the l sound is phonetically softer, perfectly fitting the cozy, gentle tone of the word.

I see wprawdzie at the start of the sentence. Do I always need to pair it with ale?

Almost always, yes. Wprawdzie comes from w prawdzie (in truth) and translates to 'admittedly' or 'it is true that'. It naturally sets up a concession, so you will usually see it paired with ale (but) or jednak (however) in the second half of the sentence to introduce the contrast.

Just to review, why do stary and cieplutki use the nominative case instead of the instrumental?