This method requires chemicals. So, ensure you wear gloves and be cautious. To tan hide with borax, use a knife to spread the borax paste on the rawhide to about 1/8 inch thick. Use your fingers to firmly rub it into the hide and leave it for about 24 hours. Scrape off the paste and apply a fresh one. You may need to repeat this process 2-3 times for the tanning process to complete.