Hi I just need some help my client has 90% White hair with very porous ends I've just used majirel 8.33 & 8.3 with 20 vol colour turned out like a very translucent 9. With no depth or hardly any colour which is what she is looking for, any ideas on what to use to help the colour take.

Quasi?

If your trying to color more than 50% white, you should mix in a base shade with your chosen shade otherwise you won't achieve 100% coverage. You didn't add the natural base 8 with your 8.33 That's why it looks translucent.
And as Bluerinse has said above, you can use a quasi on the porous ends.

However I may have misread your initial question. If so, ignore my response.

NIs it loreal you're using? If you are then 8.3 is the right base. Perhaps 8.30 and 8.3 would be better as there's more of an intensive tone. Or even 8.0 & 8.30.

You used the right colours, 8.3 is a base in majirel. On stubborn white you can drop down to 10 vol, which usually does the trick.

With 8.3 on white I still always use half 8, don't I need too ?

With loreal you dont. My nan is 100% white (whiter than snow lol) and I use 8,3 and 20vol and has covered better than anything else I've ever used on it you don't need the 8,0
Can I ask the person who started this thread why u used 8,3 with 8,33? Won't this make it extremely gold ? Its just I've never heard of it before thank u x

In majirel, you have cool bases, and golden bases (the .3's). Golden bases are the bases for adding into warm tones (the .33's, .4's, .5's and .6's) to add depth.8.33 and 8.3 mixed together will come out as a target 8.33 on white hair.
You only add the other bases to cool tones or to flatten warm tones.

Also you could try mixing equal parts oxident and colorant...haven't used l'oreal for a while but I think it was 75ml oxident per 50ml tube? Go equal parts it mean your Pigment is stronger and there's no harm in caking the hair in it!

Use Wella, I find it covers better & give more shine/coverage. Mix 10gs 8/0 & 20gs 8.3 & 30gs 20 vol & leave on for 45 minutes