Hello everyone. 

I need some help with a knife im etching. The blade etches great in some spots, but barely at all in others. Ive made quite a few damascus blades before, but ive never had this happen. For the last few hours ive been experimenting with every variable i can think of; time in acid, grit of sandpaper used to remove oxides, etc. For some reason, it simply refuses to etch properly in this one spot, on both sides of the blade. 

Any help that can be given will be appreciated. And this knife is supposed to go out to the customer tomorrow, so quick replies would be even more appreciated. Sorry if this topic seems brash and hastily written but im at my wits end here. Apologies for the bad pictures, but all i have is my phone. 

Blade is o1 and 15N20, and it is being etched in hydrochloric acid.

Thanks. 

Did you thoroughly de-grease the blade before etching? If not the could well be the problem. Other than that the only thing I can think of is that the blade isn't hardened evenly and the softer areas are etching differently to the harder areas. Hopefully its just a grease issue, Good luck!

Likely not a grease issue. I am certain it was clean. Also, there is no way its a hardness issue. I just remembered i have a pic of right after i heat treated it. Ill add it in. The only thing that changed between then and now is that i sanded it down. Thank you for your reply. 

The above pic was directly after tempering. I wanted to see the pattern, so i quickly sanded it and etched it. After that, i ground in the final edge and sanded the scratches out. Strange, huh?

Some clog-resistant long life sandpapers have a stearate  wax coat on the paper.  Did you use something  new/different to do the post hardening sanding?

Strangely enough, no. 

Is there a chance your etchant could be contaminated with a thin layer of oil on the surface of it? It almost looks like you have a tide line going across the blade as though its dragged a layer of oil with it as it's entered the acid, other than that I have no idea. I hope someone with more experience than myself can help you figure it out!

That is possible i suppose. But i would think that it would make the whole pattern not show up, not just in spots. I will take some fresh etchant in a new conatiner and give it a try. Thank you. 

I would honestly re do the heat treat to remove that portion of non martensitic steel  from the pattern

It seems Foundryman was correct. I just got back from picking up more acid and after etching in the new stuff, the whole pattern is showing again. Somehow, the old acid became contaminated, possibly in my hasty excitement to see the pattern right after heat treat, i didnt clean it properly and that resulted in contamination. I thank everybody for their replies and their help. I will post pics when the blade is finished.