Being retired, I have tons of time to torch. When I make 3/4" marbles, I usually spend 5 hours (with breaks) and get about 40 marbles completed. I use my calipers on the white base glass then add color. Making these, I spent 2 weeks totally because I made other marbles along with these but I used Morano glass instead of Kugler. Both are soft glass but Kugker is 96 and Morano is 104, Looking at the pictures of other great marbles that have been posted, I assume they most all are made using Boro.