I have a third class relic from Blessed Carlo Acutis. If I touch that item to another item, does that item become a third class relic also?
A third class relic is any item, new or old, that has made contact with the remains of a saint, or pressed against their tomb or reliquary; in other words a first class relic.1
Third-class relics: any object that has been in contact with a first- or second-class relic.2
A 3rd class relic doesn't fulfil these requirements.