IF you can prove with expert testimony from someone who examined the sparkler (e.g. a fireworks expert; some sort of chemist or chemical engineer; etc.) that the sparkler was defective AND that the defect and not some misuse on your part caused the burns, then you can establish liability. You need expert testimony for a product liability case; you, as a layperson, cannot credible comment on whether and how it was defective.However, that's only part of a viable lawsuit. The second part is damages, or what happened to you, and what you are entitled to. You write that you hand was burned; you could recover in the lawsuit your out-of-pocket (not paid by health insurnace or Medicare/caid) health costs, lost wages, if you missed work due to this, and if you have suffered significant and long lasting pain, disability, disfigurement or other life impairment--i.e. life impairment lasting several months or longer--some amount for "pain and suffering." The pain and suffering award is generally related to the  medical costs: with low medical costs, it is difficult to establish serious impairment. So unless you incurred large medical costs, missed weeks at work, and/or have some long-lasting impairment, you will not receive much money, even if you winHowever, as stated, you will have to hire an expert to conduct tests, render an opinion, and testify; you will also need, if you are trying to recover "pain and suffering," to hire a medical expert (a doctor) to testify about your injuries. Therefore, even if you act as your own attorney ("pro se") and do not hire a lawyer, you can easily spend $1,500 - $2,000 or more on court costs and expert fees, plus will lose some time away from work for the case, none of which you can get back (each party pays its own litigation expenses and cannot recover for its time spent litigating). Therefore, with--as we hope--injuries that resolved quickly and well, and only a few hundred dollars (or less) in medical costs, you could spend more on the lawsuit than you will get back.